Question

I have a simple class

class Foo {
    public:
        float m;
        Foo();
}

Foo::Foo(){
    this->m = 1.0f;
}

Then I’m extending it with

class Bar: public Foo {
    public:
        float m;
        Bar()
}

Bar::Bar(){
    this->m = 10.0f;
}

I then instantiate Bar() but Bar.m is still 1.0f. Is there a reason for this?

Answer 1

In C++, you cannot override a field. Only methods can be overridden. Consequently, your declaration of the variable m in the class Bar is a new field that hides the base class Foo‘s version of m.

If you want to access Foo‘s m from Bar, then you could use this syntax:

Bar::Bar(){
    this->Foo::m = 10.0f;
}

Which explicitly tells the compiler to write to Foo‘s version of m. Alternatively, you can drop the this-> and just write

Bar::Bar(){
    Foo::m = 10.0f;
}

Hope this helps!