[Solved] Difference between in class and constructor initialisation [closed]

Question

Under the C++11 standard, we can supply an in-class initializer for a
data member. When we create objects, the in-class initializers will be
used to initialize the data members. Members without an initializer
are default initialized.

Your first example uses an in-class initializer, while your second example only initializes a within the default constructor.

Say you have another constructor z, which takes some parameters but does not initialize data member a. Then upon calling z,

If you use in-class initializer, it will be used to set a = 3.
If you only initialize a in your default constructor, then a will be uninitialized.

Accepted Answer

Under the C++11 standard, we can supply an in-class initializer for a
data member. When we create objects, the in-class initializers will be
used to initialize the data members. Members without an initializer
are default initialized.

Your first example uses an in-class initializer, while your second example only initializes a within the default constructor.

Say you have another constructor z, which takes some parameters but does not initialize data member a. Then upon calling z,

If you use in-class initializer, it will be used to set a = 3.
If you only initialize a in your default constructor, then a will be uninitialized.