从int隐式转换为类类型

Question

I ran across some code that looked like this:

class Cents
{
private:
    int m_nCents;
public:
    Cents(int nCents) : m_nCents(nCents)
    {
    }
 };

int main(){
    Cents c = 0; // why is this possible?
}

Why is it possible to convert from int to type of class Cents? Also, is the copy constructor called in this case?

Answer 1

Why is it possible to convert from int to type of class Cents?

It is allowed because it's handy sometimes. But it may also be problematic: that's why you can forbid such implicit constructions by making the class constructor explicit .

Also, is the copy constructor called in this case?

Since it's an rvalue, the call would be to a move constructor/assignment (which could fallback to a copy ctor/assignment); but the compiler will likely omit that. If you wrote that explicitly, it would be equivalent to:

Cents c = Cents(0);