What is Serialization in MFC? How is it Implemented?

Serialization in MFC (Microsoft Foundation Class) is the process of saving and loading object data to and from a persistent storage medium, such as a file. MFC makes serialization easy by providing built-in support for serializing objects, especially in document/view architecture.

What is Serialization?

Serialization is the process of converting an object’s state into a format that can be stored (e.g., a file, database) and then reconstructed later by deserializing it.

How is Serialization Implemented in MFC?

MFC uses the `CObject` class’s `Serialize()` function to facilitate serialization. Classes that need to be serialized must inherit from `CObject` and implement the `Serialize()` method.

Steps to Implement Serialization

1. Derive the Class from CObject

Any class that needs serialization must inherit from `CObject` and use the `DECLARE_SERIAL` and `IMPLEMENT_SERIAL` macros.
“`cpp
class CMyData : public CObject
{
DECLARE_SERIAL(CMyData)

public:
int m_nData;
CString m_strData;

// Serialization
virtual void Serialize(CArchive& ar);
};
“`

2. Implement the Serialize() Method

The `Serialize()` method handles saving and loading the object data:
“`cpp
void CMyData::Serialize(CArchive& ar)
{
if (ar.IsStoring())
{
ar << m_nData << m_strData; } else { ar >> m_nData >> m_strData;
}
}
“`

3. Use Serialization in Document/View Architecture

If you’re using MFC’s document/view architecture, serialization is typically handled in the `CDocument` class:
“`cpp
void CMyDocument::Serialize(CArchive& ar)
{
m_MyData.Serialize(ar); // Call the Serialize method of CMyData
}
“`

How to Use CArchive for File Operations

MFC uses the `CArchive` class to manage reading and writing serialized data. Here’s an example of storing data:
“`cpp
CFile file(_T(“data.dat”), CFile::modeCreate | CFile::modeWrite);
CArchive ar(&file, CArchive::store);
myData.Serialize(ar); // Store data
ar.Close();
“`

Deserializing Data

To load serialized data from a file:
“`cpp
CFile file(_T(“data.dat”), CFile::modeRead);
CArchive ar(&file, CArchive::load);
myData.Serialize(ar); // Load data
ar.Close();
“`

Serialization in MFC provides a robust way to persist object data, making it a core feature in document-based applications.