Unknown name of the following: class Foo::Bar

Question

I was reading a program in c++ and came across the following

class Foo::Bar
{
   ...
}

I have been researching different methods of class implementation but have not come across the :: when creating a class. Do you know the name of it so I can look it up?

Foo is a full size class, not a namespace. I do not know what Bar is.

Thank you

Answer 1

It is a nested class definition. It means that the class Bar was declared inside class Foo. Kind of like this:

class Foo
{
...
class Bar;
...
};