CODEWITHSUNDEEP
c++
Andres Bucci
Andres Bucci

Reputation: 947

returning bool from member variable pointer

So I'm working with this code that looks like this:

class SomeClass : public SomeBaseClass {
    SomePointerToClass * p;
  public:
    SomeClass(SomePointerToClass* p = NULL) : p(p) {};
    void start(SomePointerToClass* sp) {
        p = sp;
    }
    bool hasStarted() {
        return p;
    }
}

I simplified some stuff so that I could make a short code example, but I think the returning a bool from a member variable pointer is a bit of a codesmell. Should I change it or is this some form of C++ convention?

Upvotes: 1

Views: 152

Answers (2)

Topological Sort
Topological Sort

Reputation: 2787

bool hasStarted () { return (bool) p; }

This makes it clear "I meant to do that," and is, I'd say, a very reasonable thing to do.

I sometimes do this inside a function that has access to a pointer p:

if (p) ... //meaning:  if p isn't NULL...

but the consensus is I shouldn't mention returning a pointer -- and I'm sure the consensus is correct here. So edited.

Upvotes: 0

Lightness Races in Orbit
Lightness Races in Orbit

Reputation: 385174

hasStarted() is fine: in C++, the pointer will be automatically converted to bool on a zero/not-zero basis.†

Some people prefer to write return (p != nullptr) or return static_cast<bool>(p) instead, in order to be really explicit about intent, but I'm not terribly fussy about that in cases like this.

† However, the behaviour is implementation-defined in C, so do not rely on it there!

Upvotes: 3

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