1 TObj Package {#user_guides__tobj}
6 @section occt_tobj_1 Introduction
8 This document describes the package TObj, which is an add-on
9 to the Open CASCADE Application Framework (OCAF).
11 This package provides a set of classes and auxiliary tools facilitating
12 the creation of object-oriented data models on top of low-level OCAF data structures.
15 * Definition of classes representing data objects. Data objects store their data using primitive OCAF attributes, taking advantage of OCAF mechanisms for Undo/Redo and persistence. At the same time they provide a higher level abstraction over the pure OCAF document structure (labels / attributes).
16 * Organization of the data model as a hierarchical (tree-like) structure of objects.
17 * Support of cross-references between objects within one model or among different models. In case of cross-model references the models should depend hierarchically.
18 * Persistence mechanism for storing *TObj* objects in OCAF files, which allows storing and retrieving objects of derived types without re-generating the schema.
20 This document describes basic principles of logical and physical organization
21 of TObj-based data models and typical approaches to implementation of classes representing model objects.
23 @subsection occt_tobj_1_1 Applicability
25 The main purpose of the *TObj* data model is rapid development
26 of the object-oriented data models for applications, using the existing
27 functionality provided by OCAF (Undo/Redo and persistence)
28 without the necessity to re-develop such functionality from scratch.
30 As opposed to using bare OCAF (at the level of labels and attributes),
31 TObj facilitates dealing with higher level abstracts, which are closer
32 to the application domain. It works best when the application data are naturally
33 organized in hierarchical structures, and is especially useful for complex data
34 models with dependencies between objects belonging to different parts of the model.
36 It should be noted that *TObj* is efficient for representing data structures containing
37 a limited number of objects at each level of the data structure (typically less than 1000).
38 A greater number of objects causes performance problems due to list-based organization of OCAF documents. Therefore, other methods of storage, such as arrays, are advisable for data models or their sub-parts containing a great number of uniform objects. However, these methods
39 can be combined with the usage of *TObj* to represent the high-level structure of the model.
41 @section occt_tobj_2 *TObj* Model
43 @subsection occt_tobj_2_1 *TObj* Model structure
45 In the *TObj* data model the data are separated from the interfaces that manage them.
47 It should be emphasized that *TObj* package defines only the interfaces and the basic structure of the model and objects, while the actual contents and structure of the model of a particular application are defined by its specific classes inherited from *TObj* classes. The implementation can add its own features or even change the default behaviour and the data layout, though this is not recommended.
49 Logically the *TObj* data model is represented as a tree of model objects, with upper-level objects typically being collections of other objects (called *partitions*, represented by the class *TObj_Partition*). The root object of the model is called the *Main partition* and is maintained by the model itself. This partition contains a list of sub-objects called its *children* each sub-object may contain its own children (according to its type), etc.
51 @image html /user_guides/tobj/images/tobj_image003.png "TObj Data Model"
52 @image latex /user_guides/tobj/images/tobj_image003.png "TObj Data Model"
54 As the *TObj* Data Model is based on OCAF (Open CASCADE Application Framework) technology,
55 it stores its data in the underlying OCAF document. The OCAF document consists of a tree of
56 items called *labels*. Each label has some data attached to it in the form of *attributes*,
57 and may contain an arbitrary number of sub-labels. Each sub-label is identified by its sequential
58 number called the *tag*. The complete sequence of tag numbers of the label
59 and its parents starting from the document root constitutes the complete *entry*
60 of the label, which uniquely identifies its position in the document.
62 Generally the structure of the OCAF tree of the *TObj* data
63 model corresponds to the logical structure of the model and can be presented as in the following picture:
65 @image html /user_guides/tobj/images/tobj_image004.png "TObj Data Model mapped on OCAF document"
66 @image latex /user_guides/tobj/images/tobj_image004.png "TObj Data Model mapped on OCAF document"
68 All data of the model are stored in the root label (0:1) of the OCAF document.
69 An attribute *TObj_TModel* is located in this root label. It
70 stores the object of type *TObj_Model*. This object serves as a main interface tool
71 to access all data and functionalities of the data model.
73 In simple cases all data needed by the application may be
74 contained in a single data model. Moreover, *TObj* gives the possibility to
75 distribute the data between several interconnected data models. This can be
76 especially useful for the applications dealing with great amounts of data. because
77 only the data required for the current operation is loaded in the memory at one time.
78 It is presumed that the models have a hierarchical (tree-like) structure,
79 where the objects of the child models can refer to the objects of the parent
80 models, not vice-versa. Provided that the correct order of loading and closing
81 of the models is ensured, the *TObj* classes will maintain references between the objects automatically.
83 @subsection occt_tobj_2_2 Data Model basic features
85 The class *TObj_Model* describing the data model provides the following functionalities:
87 * Loading and saving of the model from or in a file (methods *Load* and *Save*)
88 * Closing and removal of the model from memory (method *Close*)
89 * Definition of the full file name of the persistence storage for this model (method *GetFile*)
90 * Tools to organize data objects in partitions and iterate on objects (methods *GetObjects*, *GetMainPartition*, *GetChildren*, *getPartition*, *getElementPartition*)
91 * Mechanism to give unique names to model objects
92 * Copy (*clone*) of the model (methods *NewEmpty* and *Paste*)
93 * Support of earlier model formats for proper conversion of a model loaded from a file written by a previous version of the application (methods *GetFormatVersion* and *SetFormatVersion*)
94 * Interface to check and update the model if necessary (method *Update*)
95 * Support of several data models in one application. For this feature use OCAF multi-transaction manager, unique names and GUIDs of the data model (methods *GetModelName*, *GetGUID*)
97 @subsection occt_tobj_2_3 Model Persistence
99 The persistent representation of any OCAF model is contained in an XML or a binary file,
100 which is defined by the format string returned by the method *GetFormat*.
101 The default implementation works with a binary OCAF document format (*BinOcaf*).
102 The other available format is *XmlOcaf*. The class **TObj_Model** declares and provides a default
103 implementation of two virtual methods:
106 virtual Standard_Boolean Load (const char* theFile);
107 virtual Standard_Boolean SaveAs (const char* theFile);
110 which retrieve and store the model from or
111 in the OCAF file. The descendants
112 should define the following protected method to support Load and Save operations:
115 virtual Standard_Boolean initNewModel (const Standard_Boolean IsNew);
118 This method is called by *Load* after creation of a new model
119 or after its loading from the file; its purpose is to perform
120 the necessary initialization of the model (such as creation of necessary top-level
121 partitions, model update due to version changes etc.). Note that if
122 the specified file does not exist, method *Load* will create
123 a new document and call *initNewModel* with the argument **True**.
124 If the file has been normally loaded, the argument **False** is passed.
125 Thus, a new empty *TObj* model is created by calling *Load* with an empty
126 string or the path to a nonexistent file as argument.
128 The method *Load* returns **True** if the model has been retrieved successfully
129 (or created a new), or **False** if the model could not be loaded.
130 If no errors have been detected during initialization (model retrieval or creation),
131 the virtual method *AfterRetrieval* is invoked for all objects of the model.
132 This method initializes or updates the objects immediately after the model initialization.
133 It could be useful when some object data should be imported from an OCAF attribute into transient
134 fields which could be changed outside of the OCAF transaction mechanism.
135 Such fields can be stored into OCAF attributes for saving into persistent storage during the save operation.
137 To avoid memory leaks, the *TObj_Model* class destructor invokes *Close* method
138 which clears the OCAF document and removes all data from memory before the model is destroyed.
140 For XML and binary persistence of the *TObj* data model the corresponding drivers are implemented
141 in *BinLDrivers*, *BinMObj* and *XmlLDrivers*, *XmlMObj* packages.
142 These packages contain retrieval and storage drivers for the model, model objects and custom attributes
143 from the *TObj* package. The schemas support persistence for the standard OCAF and *TObj* attributes.
144 This is sufficient for the implementation of simple data models, but
145 in some cases it can be reasonable to add specific OCAF attributes to
146 facilitate the storage of the data specific to the application.
147 In this case the schema should be extended using the standard OCAF mechanism.
149 @subsection occt_tobj_2_4 Access to the objects in the model
151 All objects in the model are stored in the main partition and accessed by iterators.
152 To access all model objects use:
155 virtual Handle(TObj_ObjectIterator) GetObjects () const;
158 This method returns a recursive iterator on all objects stored in the model.
161 virtual Handle(TObj_ObjectIterator) GetChildren () const;
164 This method returns an iterator on child objects of the main partition.
165 Use the following method to get the main partition:
168 Handle(TObj_Partition) GetMainPartition() const;
171 To receive the iterator on objects of a specific type *AType* use the following call:
174 GetMainPartition()->GetChildren(STANDARD_TYPE(AType) );
177 The set of protected methods is provided for descendant classes to deal with partitions:
180 virtual Handle(TObj_Partition) getPartition (const TDF_Label, const Standard_Boolean theHidden) const;
183 This method returns (creating if necessary) a partition in the specified label of the document.
184 The partition can be created as hidden (*TObj_HiddenPartition* class).
185 A hidden partition can be useful to distinguish the data that
186 should not be visible to the user when browsing the model in the application.
188 The following two methods allow getting (creating) a partition
189 in the sub-label of the specified label in the document
190 (the label of the main partition for the second method) and with the given name:
193 virtual Handle(TObj_Partition) getPartition (const TDF_Label, const Standard_Integer theIndex, const TCollection_ExtendedString& theName, const Standard_Boolean theHidden) const;
194 virtual Handle(TObj_Partition) getPartition (const Standard_Integer theIndex, const TCollection_ExtendedString& theName, const Standard_Boolean theHidden) const;
197 If the default object naming and the name register mechanism
198 is turned on, the object can be found in the model by its unique name:
201 Handle(TObj_Object) FindObject (const Handle(TCollection_HExtendedString)& theName, const Handle(TObj_TNameContainer)& theDictionary) const;
204 @subsection occt_tobj_2_5 Own model data
206 The model object can store its own data in the Data label
207 of its main partition, however, there is no standard API for
208 setting and getting these data types. The descendants can add
209 their own data using standard OCAF methods. The enumeration DataTag is defined
210 in *TObj_Model* to avoid conflict of data labels used by this class
211 and its descendants, similarly to objects (see below).
213 @subsection occt_tobj_2_6 Object naming
215 The basic implementation of *TObj_Model* provides the default
216 naming mechanism: all objects must have unique names,
217 which are registered automatically in the data model dictionary.
218 The dictionary is a *TObj_TNameContainer*
219 attribute whose instance is located in the model root label.
220 If necessary, the developer can add several dictionaries into
221 the specific partitions, providing the name registration in the
222 correct name dictionary and restoring the name map after document is loaded from file.
223 To ignore name registering it is necessary to redefine the methods *SetName*,
224 *AfterRetrieval* of the *TObj_Object* class and skip the registration of the object name.
225 Use the following methods for the naming mechanism:
228 Standard_Boolean IsRegisteredName (const Handle(TCollection_HExtendedString)& theName, const Handle(TObj_TNameContainer)& theDictionary ) const;
231 Returns **True** if the object name is already registered in the indicated (or model) dictionary.
234 void RegisterName (const Handle(TCollection_HExtendedString)& theName, const TDF_Label& theLabel, const Handle(TObj_TNameContainer)& theDictionary ) const;
237 Registers the object name with the indicated label where the object
238 is located in the OCAF document. Note that the default implementation
239 of the method *SetName* of the object registers the new name automatically
240 (if the name is not yet registered for any other object)
243 void UnRegisterName (const Handle(TCollection_HExtendedString)& theName, const Handle(TObj_TNameContainer)& theDictionary ) const;
246 Unregisters the name from the dictionary. Ther names of *TObj* model
247 objects are removed from the dictionary when the objects are deleted from the model.
250 Handle(TObj_TNameContainer) GetDictionary() const;
253 Returns a default instance of the model dictionary (located at the model root label).
254 The default implementation works only with one dictionary.
255 If there are a necessity to have more than one dictionary for the model objects,
256 it is recommended to redefine the corresponding virtual method of TObj_Object
257 that returns the dictionary where names of objects should be registered.
259 @subsection occt_tobj_2_7 API for transaction mechanism
261 Class *TObj_Model* provides the API for transaction mechanism (supported by OCAF):
264 Standard_Boolean HasOpenCommand() const;
267 Returns True if a Command transaction is open
270 void OpenCommand() const;
273 Opens a new command transaction.
276 void CommitCommand() const;
279 Commits the Command transaction. Does nothing If there is no open Command transaction.
282 void AbortCommand() const;
285 Aborts the Command transaction. Does nothing if there is no open Command transaction.
288 Standard_Boolean IsModified() const;
291 Returns True if the model document has a modified status (has changes after the last save)
294 void SetModified( const Standard_Boolean );
297 Changes the modified status by force. For synchronization of transactions
298 within several *TObj_Model* documents use class *TDocStd_MultiTransactionManager*.
300 @subsection occt_tobj_28 Model format and version
302 Class *TObj_Model* provides the descendant classes with a means to control
303 the format of the persistent file by choosing the schema used to store or retrieve operations.
306 virtual TCollection_ExtendedString GetFormat () const;
309 Returns the string *TObjBin* or *TObjXml* indicating
310 the current persistent mechanism. The default value is *TObjBin*.
311 Due to the evolution of functionality of the developed application,
312 the contents and the structure of its data model vary from version to version.
313 *TObj* package provides a basic mechanism supporting backward versions compatibility,
314 which means that newer versions of the application will be able to read
315 Data Model files created by previous versions (but not vice-versa) with a minimum loss of data.
316 For each type of Data Model, all known versions of the data format
317 should be enumerated in increasing order, incremented with every change
318 of the model format. The current version of the model
319 format is stored in the model file and can be checked upon retrieval.
322 Standard_Integer GetFormatVersion() const;
325 Returns the format version stored in the model file
328 void SetFormatVersion(const Standard_Integer theVersion);
331 Defines the format version used for save.
333 Upon loading a model, the method *initNewModel()*, called immediately
334 after opening a model from disk (on the level of the OCAF document),
335 provides a specific code that checks the format version stored in that model.
336 If it is older than the current version of the application, the data update can be performed.
337 Each model can have its own specific conversion code
338 that performs the necessary data conversion to make them compliant with the current version.
340 When the conversion ends the user is advised of that by the messenger interface
341 provided by the model (see messaging chapter for more details),
342 and the model version is updated. If the version of data model is not supported
343 (it is newer than the current or too old), the load operation should fail.
344 The program updating the model after version change can be implemented as static
345 methods directly in C++ files of the corresponding Data Model classes,
346 not exposing it to the other parts of the application.
347 These codes can use direct access to the model and objects data (attributes)
348 not using objects interfaces, because the data model API and object classes
349 could have already been changed.
351 Note that this mechanism has been designed to maintain version compatibility
352 for the changes of data stored in the model, not for the changes of
353 low-level format of data files (such as the storage format of a specific OCAF attribute).
354 If the format of data files changes, a specific treatment on a case-by-case basis will be required.
356 @subsection occt_tobj_2_9 Model update
358 The following methods are used for model update to ensure its consistency
359 with respect to the other models in case of cross-model dependencies:
362 virtual Standard_Boolean Update();
365 This method is usually called after loading of the model.
366 The default implementation does nothing and returns **True**.
369 virtual Standard_Boolean initNewModel( const Standard_Boolean IsNew);
372 This method performs model initialization, check and updates (as described above).
375 virtual void updateBackReferences( const Handle(TObj_Object)& theObj);
378 This method is called from the previous method to update back references
379 of the indicated object after the retrieval of the model from file
380 (see data model - object relationship chapter for more details)
382 @subsection occt_tobj_2_10 Model copying
384 To copy the model between OCAF documents use the following methods:
387 virtual Standard_Boolean Paste (Handle(*TObj_Model*) theModel, Handle(TDF_RelocationTable) theRelocTable = 0 );
390 Pastes the current model to the new model. The relocation table
391 ensures correct copying of the sub-data shared by several parts of the model.
392 It stores a map of processed original objects of relevant types in their copies.
395 virtual Handle(*TObj_Model*) NewEmpty() = 0;
398 Redefines a pure virtual method to create a new empty instance of the model.
401 void CopyReferences ( const Handle(*TObj_Model*)& theTarget, const Handle(TDF_RelocationTable)& theRelocTable);
404 Copies the references from the current model to the target model.
406 @subsection occt_tobj_2_11 Messaging
408 The messaging is organised using Open CASCADE Messenger from the package Message.
409 The messenger is stored as the field of the model instance
410 and can be set and retrieved by the following methods:
413 void SetMessenger( const Handle(Message_Messenger)& );
414 Handle(Message_Messenger) Messenger() const;
417 A developer should create his own instance of the Messenger
418 bound to the application user interface, and attribute it to the model
419 for future usage. In particular the messenger is used for reporting
420 errors and warnings in the persistence mechanism.
421 Each message has a unique string identifier (key).
422 All message keys are stored in a special resource file TObj.msg.
423 This file should be loaded at the start of the application
424 by call to the appropriate method of the class *Message_MsgFile*.
426 @section occt_tobj_3 Model object
428 Class *TObj_Object* provides basic interface and default implementation
429 of important features of *TObj* model objects. This implementation defines
430 basic approaches that are recommended for all descendants,
431 and provides tools to facilitate their usage.
433 @image html /user_guides/tobj/images/tobj_image005.png "TObj objects hierarchy"
434 @image latex /user_guides/tobj/images/tobj_image005.png "TObj objects hierarchy"
436 @subsection occt_tobj_3_1 Separation of data and interface
438 In the *TObj* data model, the data are separated from the interfaces that manage them.
439 The data belonging to a model object are stored in its root label and sub-labels
440 in the form of standard OCAF attributes. This allows using standard OCAF mechanisms
441 for work with these data, and eases the implementation of the persistence mechanism.
443 The instance of the interface which serves as an API for managing object data
444 (e.g. represents the model object) is stored in the root label of the object,
445 and typically does not bring its own data. The interface classes are organized in a hierarchy
446 corresponding to the natural hierarchy of the model objects according to the application.
448 In the text below the term 'object' is used to denote either the instance
449 of the interface class or the object itself (both interface and data stored in OCAF).
451 The special type of attribute *TObj_TObject* is used for storing instances of objects interfaces
452 in the OCAF tree. *TObj_TObject* is a simple container for the object of type *TObj_Object*.
453 All objects (interfaces) of the data model inherit this class.
455 @image html /user_guides/tobj/images/tobj_image006.png "*TObj* object stored on OCAF label"
456 @image latex /user_guides/tobj/images/tobj_image006.png "*TObj* object stored on OCAF label"
459 @subsection occt_tobj_3_2 Basic features
461 The *TObj_Object* class provides some basic features that can be inherited (or, if necessary, redefined) by the descendants:
463 * Gives access to the model to which the object belongs (method *GetModel*) and to the OCAF label in which the object is stored (method *GetLabel*).
464 * Supports references (and back references) to other objects in the same or in another model (methods *getReference*, *setReference*, *addReference*, *GetReferences*, *GetBackReferences*, *AddBackReference*, *RemoveBackReference*, *ReplaceReference*)
465 * Provides the ability to contain child objects, as it is actual for partition objects (methods *GetChildren*, *GetFatherObject*)
466 * Organizes its data in the OCAF structure by separating the sub-labels of the main label intended for various kinds of data and providing tools to organize these data (see <a href="../../../../Documents%20and%20Settings/TEMP/obj-inher">below</a>). The kinds of data stored separately are:
467 * Child objects stored in the label returned by the method *GetChildLabel*
468 * References to other objects stored in the label returned by the method* GetReferenceLabel*
469 * Other data, both common to all objects and specific for each subtype of the model object, are stored in the label returned by the method *GetDataLabel*
470 * Provides unique names of all objects in the model (methods *GetDictionary*, *GetName*, *SetName*)
471 * Provides unified means to maintain persistence (implemented in descendants with the help of macros *DECLARE_TOBJOCAF_PERSISTENCE* and *IMPLEMENT_TOBJOCAF_PERSISTENCE*)
472 * Allows an object to remove itself from the OCAF document and check the depending objects can be deleted according to the back references (method *Detach*)
473 * Implements methods for identification and versioning of objects
474 * Manages the object interaction with OCAF Undo/Redo mechanism (method *IsAlive*, *AfterRetrieval*, *BeforeStoring*)
475 * Allows make a clone (methods *Clone*, *CopyReferences*, *CopyChildren*, *copyData*)
476 * Contains additional word of bit flags (methods *GetFlags*, *SetFlags*, *TestFlags*, *ClearFlags*)
477 * Defines the interface to sort the objects by rank (methods *GetOrder*, *SetOrder*)
478 * Provides a number of auxiliary methods for descendants to set/get the standard attribute values, such as int, double, string, arrays etc.
480 An object can be received from the model by the following methods:
483 static Standard_Boolean GetObj ( const TDF_Label& theLabel, Handle(TObj_Object)& theResObject, const Standard_Boolean isSuper = Standard_False );
486 Returns *True* if the object has been found in the indicated label (or in the upper level label if *isSuper* is *True*).
489 Handle(TObj_Object) GetFatherObject ( const Handle(Standard_Type)& theType = NULL ) const;
492 Returns the father object of the indicated type
493 for the current object (the direct father object if the type is NULL).
495 @subsection occt_tobj_3_3 Data layout and inheritance
497 As far as the data objects are separated from the interfaces and stored in the OCAF tree,
498 the functionality to support inheritance is required. Each object has its own data
499 and references stored in the labels in the OCAF tree. All data are stored in the sub-tree
500 of the main object label. If it is necessary to inherit a class from the base class,
501 the descendant class should use different labels for data and references than its ancestor.
503 Therefore each *TObj* class can reserve the range of tags in each of
504 *Data*, *References*, and *Child* sub-labels.
505 The reserved range is declared by the enumeration defined
506 in the class scope (called DataTag, RefTag, and ChildTag, respectively).
507 The item *First* of the enumeration of each type is defined via the *Last* item
508 of the corresponding enumeration of the parent class, thus ensuring that the tag numbers
509 do not overlap. The item *Last* of the enumeration defines the last tag reserved by this class.
510 Other items of the enumeration define the tags used for storing particular data items of the object.
511 See the declaration of the TObj_Partition class for the example.
513 *TObj_Object* class provides a set of auxiliary methods for descendants
514 to access the data stored in sub-labels by their tag numbers:
517 TDF_Label getDataLabel (const Standard_Integer theRank1, const Standard_Integer theRank2 = 0) const;
518 TDF_Label getReferenceLabel (const Standard_Integer theRank1, const Standard_Integer theRank2 = 0) const;
521 Returns the label in *Data* or *References* sub-labels at a given tag number (theRank1).
522 The second argument, theRank2, allows accessing the next level of hierarchy
523 (theRank2-th sub-label of theRank1-th data label).
524 This is useful when the data to be stored are represented by multiple OCAF attributes
525 of the same type (e.g. sequences of homogeneous data or references).
527 The get/set methods allow easily accessing the data located in the specified data label
528 for the most widely used data types (*Standard_Real*, *Standard_Integer*, *TCollection_HExtendedString*,
529 *TColStd_HArray1OfReal*, *TColStd_HArray1OfInteger*, *TColStd_HArray1OfExtendedString*).
530 For instance, methods provided for real numbers are:
533 Standard_Real getReal (const Standard_Integer theRank1, const Standard_Integer theRank2 = 0) const;
534 Standard_Boolean setReal (const Standard_Real theValue, const Standard_Integer theRank1, const Standard_Integer theRank2 = 0, const Standard_Real theTolerance = 0.) const;
537 Similar methods are provided to access references to other objects:
540 Handle(TObj_Object) getReference (const Standard_Integer theRank1, const Standard_Integer theRank2 = 0) const;
541 Standard_Boolean setReference (const Handle(TObj_Object) &theObject, const Standard_Integer theRank1, const Standard_Integer theRank2 = 0);
544 The method *addReference* gives an easy way to store a sequence of homogeneous references in one label.
547 TDF_Label addReference (const Standard_Integer theRank1, const Handle(TObj_Object) &theObject);
550 Note that while references to other objects should be defined by descendant classes
551 individually according to the type of object, *TObj_Object* provides methods
552 to manipulate (check, remove, iterate) the existing references in the uniform way, as described below.
554 @subsection occt_tobj_3_4 Persistence
556 The persistence of the *TObj* Data Model is implemented with the help
557 of standard OCAF mechanisms (a schema defining necessary plugins, drivers, etc.).
558 This implies the possibility to store/retrieve all data that are stored
559 as standard OCAF attributes., The corresponding handlers are added
560 to the drivers for *TObj*-specific attributes.
562 The special tool is provided for classes inheriting from *TObj_Object*
563 to add the new types of persistence without regeneration of the OCAF schema.
564 The class *TObj_Persistence* provides basic means for that:
566 * automatic run-time registration of object types
567 * creation of a new object of the specified type (one of the registered types)
569 Two macros defined in the file TObj_Persistence.hxx have to be included in the definition
570 of each model object class inheriting TObj_Object to activate the persistence mechanism:
573 DECLARE_TOBJOCAF_PERSISTENCE (classname, ancestorname)
576 Should be included in the private section of declaration of each class inheriting
577 *TObj_Object* (hxx file). This macro adds an additional constructor to the object class,
578 and declares an auxiliary (private) class inheriting *TObj_Persistence*
579 that provides a tool to create a new object of the proper type.
582 IMPLEMENT_TOBJOCAF_PERSISTENCE (classname)
585 Should be included in .cxx file of each object class that should be saved and restored.
586 This is not needed for abstract types of objects. This macro implements the functions
587 declared by the previous macro and creates a static member
588 that automatically registers that type for persistence.
590 When the attribute *TObj_TObject* that contains the interface object is saved,
591 its persistence handler stores the runtime type of the object class.
592 When the type is restored the handler dynamically recognizes the type
593 and creates the corresponding object using mechanisms provided by *TObj_Persistence*.
595 @subsection occt_tobj_35 Names of objects
597 All *TObj* model objects have names by which the user can refer to the object.
598 Upon creation, each object receives a default name, constructed
599 from the prefix corresponding to the object type (more precisely, the prefix is defined
600 by the partition to which the object belongs), and the index of the object in the current partition.
601 The user has the possibility to change this name. The uniqueness of the name in the model is ensured
602 by the naming mechanism (if the name is already used, it cannot be attributed to another object).
603 This default implementation of *TObj* package works with a single instance of the name container (dictionary)
604 for name registration of objects and it is enough in most simple projects.
605 If necessary, it is easy to redefine a couple of object methods
606 (for instance *GetDictionary*()) and to take care of construction and initialization of containers.
608 This functionality is provided by the following methods:
611 virtual Handle(TObj_TNameContainer) GetDictionary() const;
614 Returns the name container where the name of object should be registered.
615 The default implementation returns the model name container.
618 Handle(TCollection_HExtendedString) GetName() const;
619 Standard_Boolean GetName( TCollection_ExtendedString& theName ) const;
620 Standard_Boolean GetName( TCollection_AsciiString& theName ) const;
623 Returns the object name. The methods with in / out argument return False if the object name is not defined.
626 virtual Standard_Boolean SetName ( const Handle(TCollection_HExtendedString)& theName ) const;
627 Standard_Boolean SetName ( const Handle(TCollection_HAsciiString)& theName ) const;
628 Standard_Boolean SetName ( const Standard_CString theName ) const;
631 Attributes a new name to the object and returns **True** if the name has been attributed successfully.
632 Returns False if the name has been already attributed to another object.
633 The last two methods are short-cuts to the first one.
635 @subsection occt_tobj_36 References between objects
637 Class *TObj_Object* allows creating references to other objects in the model.
638 Such references describe relations among objects which are not adequately reflected
639 by the hierarchical objects structure in the model (parent-child relationship).
641 The references are stored internally using the attribute TObj_TReference.
642 This attribute is located in the sub-label of the referring object (called *master*)
643 and keeps reference to the main label of the referred object.
644 At the same time the referred object can maintain the back reference to the master object.
646 @image html /user_guides/tobj/images/tobj_image007.png "Objects relationship"
647 @image latex /user_guides/tobj/images/tobj_image007.png "Objects relationship"
651 The back references are stored not in the OCAF document but as a transient field
652 of the object; they are created when the model is restored from file,
653 and updated automatically when the references are manipulated.
654 The class *TObj_TReference* allows storing references between objects
655 from different *TObj* models, facilitating the construction of complex relations between objects.
657 The most used methods for work with references are:
660 virtual Standard_Boolean HasReference( const Handle(TObj_Object)& theObject) const;
663 Returns True if the current object refers to the indicated object.
666 virtual Handle(TObj_ObjectIterator) GetReferences ( const Handle(Standard_Type)& theType = NULL ) const;
669 Returns an iterator on the object references. The optional argument *theType*
670 restricts the types of referred objects, or does not if it is NULL.
673 virtual void RemoveAllReferences();
676 Removes all references from the current object.
679 virtual void RemoveReference( const Handle(TObj_Object)& theObject );
682 Removes the reference to the indicated object.
685 virtual Handle(TObj_ObjectIterator) GetBackReferences ( const Handle(Standard_Type)& theType = NULL ) const;
688 Returns an iterator on the object back references.
689 The argument theType restricts the types of master objects, or does not if it is NULL.
692 virtual void ReplaceReference ( const Handle(TObj_Object)& theOldObject, const Handle(TObj_Object)& theNewObject );
695 Replaces the reference to theOldObject by the reference to *theNewObject*.
696 The handle theNewObject may be NULL to remove the reference.
699 virtual Standard_Boolean RelocateReferences ( const TDF_Label& theFromRoot, const TDF_Label& theToRoot, const Standard_Boolean theUpdateackRefs = Standard_True );
702 Replaces all references to a descendant label of *theFromRoot*
703 by the references to an equivalent label under *theToRoot*.
704 Returns **False** if the resulting reference does not point at a *TObj_Object*.
705 Updates back references if theUpdateackRefs is **True**.
708 virtual Standard_Boolean CanRemoveReference ( const Handle(TObj_Object)& theObj) const;
711 Returns **True** if the reference can be removed and the master object
712 will remain valid (*weak* reference).
713 Returns **False** if the master object cannot be valid without the referred object (*strong* reference).
714 This affects the behaviour of objects removal from the model – if the reference cannot be removed,
715 either the referred object will not be removed, or both the referred
716 and the master objects will be removed (depends on the deletion mode in the method **Detach**)
718 @subsection occt_tobj_3_7 Creation and deletion of objects
720 It is recommended that all objects inheriting from *TObj_Object*
721 should implement the same approach to creation and deletion.
723 The object of the *TObj* data model cannot be created independently
724 of the model instance, as far as it stores the object data in OCAF data structures.
725 Therefore an object class cannot be created directly as its constructor is protected.
727 Instead, each object should provide a static method *Create*(), which accepts the model,
728 with the label, which stores the object and other type-dependent parameters
729 necessary for proper definition of the object. This method creates a new object with its data
730 (a set of OCAF attributes) in the specified label, and returns a handle to the object's interface.
732 The method *Detach*() is provided for deletion of objects from OCAF model.
733 Object data are deleted from the corresponding OCAF label; however,
734 the handle on object remains valid. The only operation available after object deletion
735 is the method *IsAlive*() checking whether the object has been deleted or not,
736 which returns False if the object has been deleted.
738 When the object is deleted from the data model, the method checks
739 whether there are any alive references to the object.
740 Iterating on references the object asks each referring (master) object
741 whether the reference can be removed. If the master object can be unlinked,
742 the reference is removed, otherwise the master object will be removed too
743 or the referred object will be kept alive. This check is performed by the method *Detach* ,
744 but the behavior depends on the deletion mode *TObj_DeletingMode*:
746 * **TObj_FreeOnly** – the object will be destroyed only if it is free, i.e. there are no references to it from other objects
747 * **TObj_KeepDepending** – the object will be destroyed if there are no strong references to it from master objects (all references can be unlinked)
748 * **TObj_Force** – the object and all depending master objects that have strong references to it will be destroyed.
750 The most used methods for object removing are:
753 virtual Standard_Boolean CanDetachObject (const TObj_DeletingMode theMode = TObj_FreeOnly );
756 Returns **True** if the object can be deleted with the indicated deletion mode.
759 virtual Standard_Boolean Detach ( const TObj_DeletingMode theMode = TObj_FreeOnly );
762 Removes the object from the document if possible
763 (according to the indicated deletion mode).
764 Unlinks references from removed objects.
765 Returns **True** if the objects have been successfully deleted.
767 @subsection occt_tobj_3_8 Transformation and replication of object data
769 *TObj_Object* provides a number of special virtual methods to support replications of objects. These methods should be redefined by descendants when necessary.
772 virtual Handle(TObj_Object) Clone (const TDF_Label& theTargetLabel, Handle(TDF_RelocationTable) theRelocTable = 0);
775 Copies the object to theTargetLabel. The new object will have all references of its original.
776 Returns a handle to the new object (null handle if fail). The data are copied directly,
777 but the name is changed by adding the postfix *_copy*.
778 To assign different names to the copies redefine the method:
781 virtual Handle(TCollection_HExtendedString) GetNameForClone ( const Handle(TObj_Object)& ) const;
784 Returns the name for a new object copy. It could be useful to return the same object name
785 if the copy will be in the other model or in the other partition with its own dictionary.
786 The method *Clone* uses the following public methods for object data replications:
789 virtual void CopyReferences (const const Handle(TObj_Object)& theTargetObject, const Handle(TDF_RelocationTable) theRelocTable);
792 Adds to the copy of the original object its references.
795 virtual void CopyChildren (TDF_Label& theTargetLabel, const Handle(TDF_RelocationTable) theRelocTable);
798 Copies the children of an object to the target child label.
800 @subsection occt_tobj_3_9 Object flags
802 Each instance of *TObj_Object* stores a set of bit flags,
803 which facilitate the storage of auxiliary logical information assigned to the objects
804 (object state). Several typical state flags are defined in the enumeration *ObjectState*:
806 * ObjectState_Hidden – the object is marked as hidden
807 * ObjectState_Saved – the object has (or should have) the corresponding saved file on disk
808 * ObjectState_Imported – the object is imported from somewhere
809 * ObjectState_ImportedByFile – the object has been imported from file and should be updated to have correct relations with other objects
810 * ObjectState_Ordered – the partition contains objects that can be ordered.
812 The user (developer) can define any new flags in descendant classes.
813 To set/get an object, the flags use the following methods:
816 Standard_Integer GetFlags() const;
817 void SetFlags( const Standard_Integer theMask );
818 Stadnard_Boolean TestFlags( const Standard_Integer theMask ) const;
819 void ClearFlags( const Standard_Integer theMask = 0 );
822 In addition, the generic virtual interface stores the logical properties
823 of the object class in the form of a set of bit flags.
824 Type flags can be received by the method:
827 virtual Standard_Integer GetTypeFlags() const;
830 The default implementation returns the flag **Visible**
831 defined in the enumeration *TypeFlags*. This flag is used to define visibility
832 of the object for the user browsing the model (see class *TObj_HiddenPartition*).
833 Other flags can be added by the applications.
835 @subsection occt_tobj_310 Partitions
837 The special kind of objects defined by the class *TObj_Partition*
838 (and its descendant *TObj_HiddenPartition*) is provided for partitioning
839 the model into a hierarchical structure. This object represents the container
840 of other objects. Each *TObj* model contains the main partition that is placed
841 in the same OCAF label as the model object, and serves as a root of the object's tree.
842 A hidden partition is a simple partition with a predefined hidden flag.
844 The main partition object methods:
847 TDF_Label NewLabel() const;
850 Allocates and returns a new label for creation of a new child object.
853 void SetNamePrefix ( const Handle(TCollection_HExtendedString)& thePrefix);
856 Defines the prefix for automatic generation of names of the newly created objects.
859 Handle(TCollection_HExtendedString) GetNamePrefix() const;
862 Returns the current name prefix.
865 Handle(TCollection_HExtendedString) GetNewName ( const Standard_Boolean theIsToChangeCount) const;
868 Generates the new name and increases the internal counter of child objects if theIsToChangeCount is **True**.
871 Standard_Integer GetLastIndex() const;
874 Returns the last reserved child index.
877 void SetLastIndex( const Standard_Integer theIndex );
880 Sets the last reserved index.
882 @section occt_tobj_4 Auxiliary classes
884 Apart from the model and the object, package *TObj* provides a set of auxiliary classes:
886 * *TObj_Application* - defines OCAF application supporting existence and operation with *TObj* documents.
887 * *TObj_Assistant* – class provides an interface to the static data to be used during save and load operations on models. In particular, in case of cross-model dependencies it allows passing information on the parent model to the OCAF loader to correctly resolve the references when loading a dependent model.
888 * *TObj_TReference* - OCAF attribute describes the references between objects in the *TObj* model(s). This attribute stores the label of the referred model object, and provides transparent cross-model references. At runtime, these references are simple Handles; in persistence mode, the cross-model references are automatically detected and processed by the persistence mechanism of *TObj_TReference* attribute.
889 * Other classes starting with *TObj_T...* - define OCAF attributes used to store TObj-specific classes and some types of data on OCAF labels.
890 * Iterators – a set of classes implementing *TObj_ObjectIterator* interface, used for iterations on *TObj* objects:
891 * *TObj_ObjectIterator* – a basic abstract class for other *TObj* iterators. Iterates on *TObj_Object* instances.
892 * *TObj_LabelIterator* – iterates on object labels in the *TObj* model document
893 * *TObj_ModelIterator* – iterates on all objects in the model. Works with sequences of other iterators.
894 * *TObj_OcafObjectIterator* – Iterates on *TObj* data model objects. Can iterate on objects of a specific type.
895 * *TObj_ReferenceIterator* – iterates on object references.
896 * *TObj_SequenceIterator* – iterates on a sequence of *TObj* objects.
897 * *TObj_CheckModel* - a tool that checks the internal consistency of the model. The basic implementation checks only the consistency of references between objects.
899 The structure of *TObj* iterators hierarchy is presented below:
901 @image html /user_guides/tobj/images/tobj_image008.png "Hierarchy of iterators"
902 @image latex /user_guides/tobj/images/tobj_image008.png "Hierarchy of iterators"
905 @section occt_tobj_5 Packaging
907 The *TObj* sources are distributed in the following packages:
909 * *TObj* - defines basic classes that implement *TObj* interfaces for OCAF-based modelers.
910 * *BinLDrivers, XmlLDrivers* – binary and XML driver of *TObj* package
911 * *BinLPlugin, XmlLPlugin* – plugin for binary and XML persistence
912 * *BinMObj, XmlMObj* – binary and XML drivers to store and retrieve specific *TObj* data to or from OCAF document
913 * *TKBinL, TKXmlL* – toolkits of binary and XML persistence