CObject Class

Artículo
06/05/2017

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The latest version of this topic can be found at CObject Class.

The principal base class for the Microsoft Foundation Class Library.

Syntax

class AFX_NOVTABLE CObject

Members

Protected Constructors

Name	Description
CObject::CObject	Default constructor.

Public Methods

Name	Description
CObject::AssertValid	Validates this object's integrity.
CObject::Dump	Produces a diagnostic dump of this object.
CObject::GetRuntimeClass	Returns the `CRuntimeClass` structure corresponding to this object's class.
CObject::IsKindOf	Tests this object's relationship to a given class.
CObject::IsSerializable	Tests to see whether this object can be serialized.
CObject::Serialize	Loads or stores an object from/to an archive.

Public Operators

Name	Description
CObject::operator delete	Special delete operator.
CObject::operator new	Special new operator.

Remarks

It serves as the root not only for library classes such as CFile and CObList, but also for the classes that you write. CObject provides basic services, including

Serialization support
Run-time class information
Object diagnostic output
Compatibility with collection classes

Note that CObject does not support multiple inheritance. Your derived classes can have only one CObject base class, and that CObject must be leftmost in the hierarchy. It is permissible, however, to have structures and non- CObject-derived classes in right-hand multiple-inheritance branches.

You will realize major benefits from CObject derivation if you use some of the optional macros in your class implementation and declarations.

The first-level macros, [DECLARE_DYNAMIC]--brokenlink--(../Topic/not%20found.md#declare_dynamic and [IMPLEMENT_DYNAMIC]--brokenlink--(../Topic/not%20found.md#implement_dynamic), permit run-time access to the class name and its position in the hierarchy. This, in turn, allows meaningful diagnostic dumping.

The second-level macros, [DECLARE_SERIAL]--brokenlink--(../Topic/not%20found.md#declare_serial and [IMPLEMENT_SERIAL]--brokenlink--(../Topic/not%20found.md#implement_serial), include all the functionality of the first-level macros, and they enable an object to be "serialized" to and from an "archive."

For information about deriving Microsoft Foundation classes and C++ classes in general and using CObject, see Using CObject and Serialization.

Inheritance Hierarchy

CObject

Requirements

Header: afx.h

CObject::AssertValid

Validates this object's integrity.

virtual void AssertValid() const;

Remarks

AssertValid performs a validity check on this object by checking its internal state. In the Debug version of the library, AssertValid may assert and thus terminate the program with a message that lists the line number and filename where the assertion failed.

When you write your own class, you should override the AssertValid function to provide diagnostic services for yourself and other users of your class. The overridden AssertValid usually calls the AssertValid function of its base class before checking data members unique to the derived class.

Because AssertValid is a const function, you are not permitted to change the object state during the test. Your own derived class AssertValid functions should not throw exceptions but rather should assert whether they detect invalid object data.

The definition of "validity" depends on the object's class. As a rule, the function should perform a "shallow check." That is, if an object contains pointers to other objects, it should check to see whether the pointers are not null, but it should not perform validity testing on the objects referred to by the pointers.

Example

See CObList::CObList for a listing of the CAge class used in all CObject examples.

void CAge::AssertValid() const
{
   CObject::AssertValid();
   ASSERT(m_years > 0); 
   ASSERT(m_years < 105);
}

For another example, see [AfxDoForAllObjects]--brokenlink--(../Topic/not%20found.md#afxdoforallobjects).

CObject::CObject

These functions are the standard CObject constructors.

CObject();  
CObject(const CObject& objectSrc);
```  
  
### Parameters  
 *objectSrc*  
 A reference to another `CObject`  
  
### Remarks  
 The default version is automatically called by the constructor of your derived class.  
  
 If your class is serializable (it incorporates the `IMPLEMENT_SERIAL` macro), then you must have a default constructor (a constructor with no arguments) in your class declaration. If you do not need a default constructor, declare a private or protected "empty" constructor. For more information, see [Using CObject](../Topic/Using%20CObject.md).  
  
 The standard C++ default class copy constructor does a member-by-member copy. The presence of the private `CObject` copy constructor guarantees a compiler error message if the copy constructor of your class is needed but not available. You must therefore provide a copy constructor if your class requires this capability.  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in the `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#8](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#8)]  
  
##  <a name="cobject__dump"></a>  CObject::Dump  
 Dumps the contents of your object to a [CDumpContext](../Topic/CDumpContext%20Class.md) object.

virtual void Dump(CDumpContext& dc) const;

  
### Parameters  
 `dc`  
 The diagnostic dump context for dumping, usually `afxDump`.  
  
### Remarks  
 When you write your own class, you should override the `Dump` function to provide diagnostic services for yourself and other users of your class. The overridden `Dump` usually calls the `Dump` function of its base class before printing data members unique to the derived class. `CObject::Dump` prints the class name if your class uses the `IMPLEMENT_DYNAMIC` or `IMPLEMENT_SERIAL` macro.  
  
> [!NOTE]
>  Your `Dump` function should not print a newline character at the end of its output.  
  
 `Dump` calls make sense only in the Debug version of the Microsoft Foundation Class Library. You should bracket calls, function declarations, and function implementations with **#ifdef _DEBUG**/ `#endif` statements for conditional compilation.  
  
 Since `Dump` is a **const** function, you are not permitted to change the object state during the dump.  
  
 The [CDumpContext insertion (<<) operator](../Topic/CDumpContext%20Class.md#cdumpcontext__operator__lt__lt_) calls `Dump` when a `CObject` pointer is inserted.  
  
 `Dump` permits only "acyclic" dumping of objects. You can dump a list of objects, for example, but if one of the objects is the list itself, you will eventually overflow the stack.  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in all `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#9](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#9)]  
  
##  <a name="cobject__getruntimeclass"></a>  CObject::GetRuntimeClass  
 Returns the `CRuntimeClass` structure corresponding to this object's class.

virtual CRuntimeClass* GetRuntimeClass() const;

  
### Return Value  
 A pointer to the [CRuntimeClass](../Topic/CRuntimeClass%20Structure.md) structure corresponding to this object's class; never **NULL**.  
  
### Remarks  
 There is one `CRuntimeClass` structure for each `CObject`-derived class. The structure members are as follows:  
  
- **LPCSTR m_lpszClassName** A null-terminated string containing the ASCII class name.  
  
- **int m_nObjectSize** The size of the object, in bytes. If the object has data members that point to allocated memory, the size of that memory is not included.  
  
- **UINT m_wSchema** The schema number ( – 1 for nonserializable classes). See the [IMPLEMENT_SERIAL]--brokenlink--(../Topic/not%20found.md#implement_serial) macro for a description of schema number.  
  
- **CObject\* ( PASCAL\* m_pfnCreateObject )( )** A function pointer to the default constructor that creates an object of your class (valid only if the class supports dynamic creation; otherwise, returns **NULL**).  
  
- **CRuntimeClass\* ( PASCAL\* m_pfn_GetBaseClass )( )** If your application is dynamically linked to the AFXDLL version of MFC, a pointer to a function that returns the `CRuntimeClass` structure of the base class.  
  
- **CRuntimeClass\* m_pBaseClass** If your application is statically linked to MFC, a pointer to the `CRuntimeClass` structure of the base class.  
  
 This function requires use of the [IMPLEMENT_DYNAMIC]--brokenlink--(../Topic/not%20found.md#implement_dynamic, [IMPLEMENT_DYNCREATE]--brokenlink--(../Topic/not%20found.md#implement_dyncreate), or [IMPLEMENT_SERIAL]--brokenlink--(../Topic/not%20found.md#implement_serial) macro in the class implementation. You will get incorrect results otherwise.  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in all `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#10](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#10)]  
  
##  <a name="cobject__iskindof"></a>  CObject::IsKindOf  
 Tests this object's relationship to a given class.

BOOL IsKindOf(const CRuntimeClass* pClass) const;

  
### Parameters  
 `pClass`  
 A pointer to a [CRuntimeClass](../Topic/CRuntimeClass%20Structure.md) structure associated with your `CObject`-derived class.  
  
### Return Value  
 Nonzero if the object corresponds to the class; otherwise 0.  
  
### Remarks  
 This function tests `pClass` to see if (1) it is an object of the specified class or (2) it is an object of a class derived from the specified class. This function works only for classes declared with the [DECLARE_DYNAMIC]--brokenlink--(../Topic/not%20found.md#declare_dynamic), [DECLARE_DYNCREATE]--brokenlink--(../Topic/not%20found.md#declare_dyncreate, or [DECLARE_SERIAL]--brokenlink--(../Topic/not%20found.md#declare_serial) macro.  
  
 Do not use this function extensively because it defeats the C++ polymorphism feature. Use virtual functions instead.  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in all `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#11](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#11)]  
  
##  <a name="cobject__isserializable"></a>  CObject::IsSerializable  
 Tests whether this object is eligible for serialization.

BOOL IsSerializable() const;

  
### Return Value  
 Nonzero if this object can be serialized; otherwise 0.  
  
### Remarks  
 For a class to be serializable, its declaration must contain the [DECLARE_SERIAL]--brokenlink--(../Topic/not%20found.md#declare_serial) macro, and the implementation must contain the [IMPLEMENT_SERIAL]--brokenlink--(../Topic/not%20found.md#implement_serial) macro.  
  
> [!NOTE]
>  Do not override this function.  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in all `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#12](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#12)]  
  
##  <a name="cobject__operator_delete"></a>  CObject::operator delete  
 For the Release version of the library, operator **delete** frees the memory allocated by operator **new**.

void PASCAL operator delete(void* p);

void PASCAL operator delete( void* p, void* pPlace);

void PASCAL operator delete( void* p,
LPCSTR lpszFileName,
int nLine);

  
### Remarks  
 In the Debug version, operator **delete** participates in an allocation-monitoring scheme designed to detect memory leaks.  
  
 If you use the code line  
  
 [!CODE [NVC_MFCCObjectSample#14](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#14)]  
  
 before any of your implementations in a .CPP file, then the third version of **delete** will be used, storing the filename and line number in the allocated block for later reporting. You do not have to worry about supplying the extra parameters; a macro takes care of that for you.  
  
 Even if you do not use `DEBUG_NEW` in Debug mode, you still get leak detection, but without the source-file line-number reporting described above.  
  
 If you override operators **new** and **delete**, you forfeit this diagnostic capability.  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in the `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#15](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#15)]  
  
##  <a name="cobject__operator_new"></a>  CObject::operator new  
 For the Release version of the library, operator **new** performs an optimal memory allocation in a manner similar to `malloc`.

void* PASCAL operator new(size_t nSize);
void* PASCAL operator new(size_t, void* p);

void* PASCAL operator new( size_t nSize,
LPCSTR lpszFileName,
int nLine);

  
### Remarks  
 In the Debug version, operator **new** participates in an allocation-monitoring scheme designed to detect memory leaks.  
  
 If you use the code line  
  
 [!CODE [NVC_MFCCObjectSample#14](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#14)]  
  
 before any of your implementations in a .CPP file, then the second version of **new** will be used, storing the filename and line number in the allocated block for later reporting. You do not have to worry about supplying the extra parameters; a macro takes care of that for you.  
  
 Even if you do not use `DEBUG_NEW` in Debug mode, you still get leak detection, but without the source-file line-number reporting described above.  
  
> [!NOTE]
>  If you override this operator, you must also override **delete**. Do not use the standard library **_new_handler** function.  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in the `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#16](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#16)]  
  
##  <a name="cobject__serialize"></a>  CObject::Serialize  
 Reads or writes this object from or to an archive.

virtual void Serialize(CArchive& ar);

  
### Parameters  
 `ar`  
 A `CArchive` object to serialize to or from.  
  
### Remarks  
 You must override `Serialize` for each class that you intend to serialize. The overridden `Serialize` must first call the `Serialize` function of its base class.  
  
 You must also use the [DECLARE_SERIAL]--brokenlink--(../Topic/not%20found.md#declare_serial) macro in your class declaration, and you must use the [IMPLEMENT_SERIAL]--brokenlink--(../Topic/not%20found.md#implement_serial) macro in the implementation.  
  
 Use [CArchive::IsLoading](../Topic/CArchive%20Class.md#carchive__isloading) or [CArchive::IsStoring](../Topic/CArchive%20Class.md#carchive__isstoring) to determine whether the archive is loading or storing.  
  
 `Serialize` is called by [CArchive::ReadObject](../Topic/CArchive%20Class.md#carchive__readobject) and [CArchive::WriteObject](../Topic/CArchive%20Class.md#carchive__writeobject). These functions are associated with the `CArchive` insertion operator ( **<<**) and extraction operator ( **>>**).  
  
 For serialization examples, see the article [Serialization: Serializing an Object](../Topic/Serialization:%20Serializing%20an%20Object.md).  
  
### Example  
 See [CObList::CObList](../Topic/CObList%20Class.md#coblist__coblist) for a listing of the `CAge` class used in all `CObject` examples.  
  
 [!CODE [NVC_MFCCObjectSample#13](../CodeSnippet/VS_Snippets_Cpp/NVC_MFCCObjectSample#13)]  
  
## See Also  
 [Hierarchy Chart](../Topic/Hierarchy%20Chart.md)

Compartir a través de

CObject Class

Syntax

Members

Protected Constructors

Public Methods

Public Operators

Remarks

Inheritance Hierarchy

Requirements

CObject::AssertValid

Remarks

Example

CObject::CObject

Recursos adicionales