What is the correct way to initialize the vector member variable of the class?

[waschbaer]

What is the correct way to initialize the vector member variable of the class? Do we have to initialize it at all?

// Method one
class ClassName
{
public:
    ClassName() : m_vecInts() {}

private:
    std::vector<int> m_vecInts;
}

// Method two
class ClassName
{
public:
    ClassName() {} // do nothing

private:
    std::vector<int> m_vecInts;
}

I have an answer from internet: I hope there is someone could help me to understand this:)

Default initialization is performed in three situations:

1 when a variable with automatic storage duration is declared with no initializer
2 when an object with dynamic storage duration is created by a new-expression without an initializer
3 when a base class or a non-static data member is not mentioned in a constructor initializer list and that constructor is called.

The effects of default initialization are:

1 If T is a class type, the default constructor is called to provide the initial value for the new object.
2 If T is an array type, every element of the array is default-initialized.
3 Otherwise, nothing is done.

Since std::vector is a class type its default constructor is called. So the manual initialization isn't needed.

[Repeater]

No initialisation needed. It's a fully formed size zero vector, ready to go.