Question

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Nonstatic member as a default argument of a nonstatic member function
Why can member variables not be used as defaults for parameters?

Ok I apologize in advance if I am not seeing something very simplistic here or forgetting some fundamental rule of C++ but I am not sure why this does not work as expected.

Here is a example of code that I can’t get to work

class Foo
{
private:
    Bar *ptrBar;
public:
    void doSomething(int x, Bar *p = ptrBar);
}

The compiler is having an issue with the default parameter to this function. Is there some reason why this wouldn’t work.

Basically doSomething would do some operation on a Bar object, and I want it to be the one pointed to by ptrBar by default. Everything seems sound unless I am forgetting something?

Answer 1

At the time the compiler is evaluating this, ptrBar is not set. Therefore your default parameter has no default value.

Why not use a default of null and if p in doSomething() is null then use the ptrBar member.