Question

what i have is two classes

//class A is a kind of config-class which have configuration details 
//for class B
class A{
//....
};

class B{
public:
B(A const& _a)
:a(_a){}

private:
A const& a;
};

till this point everything is fine.

now i want is a B::configure(A const& _a) function so that i can dynamically pass the reference of configuration class A to class B which shall be assigned to the member variable a. but i’m not able to change the member variable B::a as it is a const&.

what can be the work around?

i think @Seth Carnegie’s approach is better, i should use a pointer to class A inside class B in this way:

 class B{
    public:
    B(A const& _a)
    :a(_a){}
    configure(A const& _a)
    { a = &_a; }    
    private:
    A const* a;
    };

Answer 1

You cannot alter a reference after it’s been initialized, whether it is const or not. The const just keeps you from making alterations to the variable that the reference refers to. So to change the variable after the instance has been constructed, you’ll have to use pointers rather than references.

Your grammar was rather unclear, tell me if I misunderstood the question.