Is it wrong to use C++ 'using' keyword in a header file?

Question

I\'ve been told it\'s bad to have \"using namespace ns123\" in a header file, but I can\'t remember what the reason given was. Is it in fact a bad thing to do, and why?

Answer 1

Pulling all the classes and functions out of their namespace is generally a bad idea and is actually opposed to concept of having namespaces...it is usually better to use 'using' on a specific class or function.