When and Why Should We Use Member Initialization Lists in C Constructors?

Member Initialization List in C Constructors

In C , a colon followed by a list of assignments within a constructor's definition is known as a member initialization list. It enables you to specify initial values for class member variables during object creation.

In the provided code snippet:

class MyClass {
public:
    MyClass() : m_classID(-1), m_userdata(0) {}
    int m_classID;
    void *m_userdata;
};

The member initialization list : m_classID(-1), m_userdata(0) assigns the initial values -1 to m_classID and 0 to m_userdata upon object creation. This is equivalent to writing:

MyClass() {
    m_classID = -1;
    m_userdata = 0;
}

Unlike variable assignments within the constructor body, member initialization list ensures that these specific member variables are initialized before executing any other code in the constructor. This is essential in scenarios where specific initial values are required for the proper functioning of the class.

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