Name hiding in constructor initialization list

Question

I want to modify a constructor to use an initialization list as in the following example:

class Foo
{
public:
   Foo(std::wstring bar);
private:
   std::wstring bar;
};

// VERSION 1:

Foo::Foo(std::wstring bar) {this->bar = bar}

// VERSION 2:

Foo::Foo(std::wstring bar) : this->bar(bar) {} // ERROR!

Unfortunately I can't do version 2 because you can't use the this pointer for data members since (I'm guessing) they don't exist yet at that point. How then, do I deal with the name hiding issue (i.e. my parameter and my data member have the same name)?

Answer 1

You don't need to. The first bar will refer to the member and the second bar will refer to the argument:

Foo::Foo(std::wstring bar) : bar(bar) {}

Answer 2

I would change the name of the argument so it's clear which is which.

Foo::Foo(std::wstring b) : bar(b) {}

Note that you don't strictly have to, but future maintainers of your code will probably thank you.

Alternate option:

It's common in C++ to denote private member variables with a special naming convention, for example a trailing underscore. That solves this problem nicely:

class Foo
{
public:
   Foo(std::wstring bar);
private:
   std::wstring bar_;
};

Foo::Foo(std::wstring bar) : bar_(bar) {}

Answer 3

You can actually do this:

Foo::Foo(std::wstring bar) : bar(bar) {}

Everything initializer used after the : must refer to either a base class or some member. That means your bar member won't be hidden at that point.

Answer 4

The compiler will know what to do... just remove this->