Question

I am working on a c++ library which is split up into multiple namespaces. Since I am trying to avoid the “using” directive in header files I am forced to do the alternative “namespace::class” for variables, returns and parameters. As you can imagine this could get messy. So, I tried putting the using statement inside a namespace decloration (see below) and that seemed to do the trick, It doesn’t appear to be visible in files including this file.

namespace Project
{
    namespace Utility { class A; }

namespace System
{
    using Utility::A;

    class B
    {
        A *a;   // instead of Utility::A *a
    };
}
}

My question is, would it be okay to do this instead?

Answer 1

// your header

namespace Project
{
    namespace Utility { class A; }

namespace System
{
    using Utility::A;

    class B
    {
        A *a;   // instead of Utility::A *a
    };
}
}

// end your header

class A {};

int main()
{
    using namespace Project::System;
    A a;
}

test.cpp:25:5: error: reference to 'A' is ambiguous
    A a;
    ^
test.cpp:20:7: note: candidate found by name lookup is 'A'
class A {};
      ^
test.cpp:9:20: note: candidate found by name lookup is 'Project::System::A'
    using Utility::A;
                   ^
1 error generated.