C ++赋值与删除的赋值运算符一起工作吗？

Question

I have a piece of code that looks something like this:

class B
{
private:
    const A& obj;
    size_t val;

    // private - prohibited
    B& operator=(const B& other);

public:
    B(const A& obj_): obj(obj_)
    {
        val = 0;
    }
};

class C
{
    void func()
    {
        A a1;
        B b1(a1);
        B b2 = b1; // should throw error?
    }
}

Class B has a private assignment operator. Nonetheless assignment in C::func() compiles without errors. But how?

Answer 1

B b2 = b1 does not use the assignment operator, because it's not assignment , it's copy initialization - using constructor, not assignment operator.

See also copy initialization

Answer 2

That's the copy constructor getting called, not the assignment operator.

The reason being is that when you initialize a variable, a constructor (in this case, the copy constructor) gets called.

B b2 = b1; // construction

This is different from assignment

b2 = b1; // b2 is already declared, so assignment

To stop this behavior, just delete your copy constructor.