How to serialize a large standard library map with custom types using Qt?

Serialization in Qt

When using the Qt library for GUI programming, you may encounter the need to serialize large standard library mappings situation. "MyType" is a class with fields of different types. What features does Qt provide to enable serialization of mappings?

Use QDataStream for serialization

QDataStream can handle various C and Qt data types, including STL containers. A detailed list of supported data types can be found in the Qt documentation. In order to implement the serialization of custom types, we need to overload the << and >> operators. The following is a custom data type definition that can be used with QDataStream:

class Painting
{
public:
    // ...
};

QDataStream &operator<<(QDataStream &out, const Painting &painting);
QDataStream &operator>>(QDataStream &in, Painting &painting);

By overloading the << operator, we can write custom data out to the stream:

QDataStream &operator<<(QDataStream &out, const Painting &painting)
{
    // ...
    return out;
}

By overloading the >> operator, we can read custom data from the stream:

QDataStream &operator>>(QDataStream &in, Painting &painting)
{
    // ...
    return in;
}

By overloading these operators, we can seamlessly combine custom types with Used together with QDataStream to implement mapping serialization and deserialization.

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