Question

I come from a Java background, where packages are used, not namespaces. I’m used to putting classes that work together to form a complete object into packages, and then reusing them later from that package. But now I’m working in C++.

How do you use namespaces in C++? Do you create a single namespace for the entire application, or do you create namespaces for the major components? If so, how do you create objects from classes in other namespaces?

Answer 1

Namespaces are packages essentially. They can be used like this:

namespace MyNamespace {   class MyClass   {   }; } 

Then in code:

MyNamespace::MyClass* pClass = new MyNamespace::MyClass(); 

Or, if you want to always use a specific namespace, you can do this:

using namespace MyNamespace;  MyClass* pClass = new MyClass(); 

Edit: Following what bernhardrusch has said, I tend not to use the ‘using namespace x’ syntax at all, I usually explicitly specify the namespace when instantiating my objects (i.e. the first example I showed).

And as you asked below, you can use as many namespaces as you like.