Question

I have some code which use ‘this’ pointer of class which calls this code. For example:

Some::staticFunction<templateType>(bind(FuncPointer, this, _1));

Here is I’m calling bind function from boost. But it doesn’t matter. Now I have to wrap this code. I made a macro:

#define DO(Type, Func) Some::staticFunction<Type>(bind(FuncPointer, this, _1));

And compiler insert this code into class which calls this macro, so ‘this’ takes from caller. But I don’t want to use macro and prefer function (inline). But how to resolve ‘this’ passing. Could I use it in inline function like in macro or I have to pass it manually?

Answer 1

The this keyword can be put by the function you call

class MyClass {
  // ...
  template<typename Type, typename Func>
  void doit(Func f) {
    Some::staticFunction<Type>(bind(f, this, _1));
  }
};

After which you can call

doit<templateType>(FuncPointer);

---

If you like you can inherit the function

// T must be a derived class of MyRegister<T>
template<typename T>
class MyRegister {
protected:
  template<typename Type, typename Func>
  void doit(Func f) {
    Some::staticFunction<Type>(bind(f, (T*)this, _1));
  }
};

class MyClass : MyRegister<MyClass> {
  // ...
};

That way you can just use doit and not first write it, just like with the macro. Useful if you have a wide range of classes that you use the function in.

Edit: Notice that the C-Style cast is required here (can’t use static_cast), because of the private inheritance. It’s a safe cast if T is derived from MyRegister<T>

---

Personally i would prefer this over the macro. Notice that your macro can’t cope with commas in the type-name

DO(std::pair<A, B>, g);

This tries to pass 3 arguments to the macro instead of 2. You could reverse the order of the type and the function and use variadic macros (which are a C++0x feature, but available in some compiler in C++03 mode) or you could use a typedef and pass the alias name.