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Learn more about: Storing and Loading CObjects via an Archive |
Storing and Loading CObjects via an Archive |
11/04/2016 |
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a829b6dd-bc31-47e0-8108-fbb946722db9 |
Storing and loading CObjects via an archive requires extra consideration. In certain cases, you should call the Serialize function of the object, where the CArchive object is a parameter of the Serialize call, as opposed to using the << or >> operator of the CArchive. The important fact to keep in mind is that the CArchive >> operator constructs the CObject in memory based on CRuntimeClass information previously written to the file by the storing archive.
Therefore, whether you use the CArchive << and >> operators, versus calling Serialize, depends on whether you need the loading archive to dynamically reconstruct the object based on previously stored CRuntimeClass information. Use the Serialize function in the following cases:
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When deserializing the object, you know the exact class of the object beforehand.
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When deserializing the object, you already have memory allocated for it.
Caution
If you load the object using the Serialize function, you must also store the object using the Serialize function. Don't store using the CArchive << operator and then load using the Serialize function, or store using the Serialize function and then load using CArchive >> operator.
The following example illustrates the cases:
[!code-cppNVC_MFCSerialization#36] [!code-cppNVC_MFCSerialization#37]
In summary, if your serializable class defines an embedded CObject as a member, you should not use the CArchive << and >> operators for that object, but should call the Serialize function instead. Also, if your serializable class defines a pointer to a CObject (or an object derived from CObject) as a member, but constructs this other object in its own constructor, you should also call Serialize.