在头文件的私有名称空间中使用声明 [英] Using declarations in private namespaces in header files

问题描述

我有一个模板类，该模板类在其方法中使用一些boost函数.由于此类是模板，因此其方法应在头文件中实现.我使用一些using声明使代码更具可读性:

I have a template class that uses some boost functions in it's methods. Cause this class is template, it's method should be implemented in a header file. I use some using declarations to make code more readable:

namespace network { 
namespace v1 {
  namespace detail {
    using boost::phoenix::if_;
    using boost::for_each;
    /* some more functions */

    template <class T>
    class Some {
      public:
        Some() {
          for_each(inVector, /* some phoenix code */);
        }
      private:
        vector<int> intVector;
    };
  }

  template <class T> using Some = detail::Some<T>;
}
}

以这种方式在标头中使用using是否安全?我认为没有人会在.cpp文件中使用using namespace network::v1::detail;，所以我不希望添加到详细名称空间的函数会导致任何名称冲突.我错了吗?

Is it safe to use using in a header this way? I don't think somebody would ever use using namespace network::v1::detail; in a .cpp file, so I don't expect functions added to detail namespace would cause any name collisions. Am I wrong?

推荐答案

是的，它很安全. using声明仅将boost函数添加到detail命名空间.您基本上回答了自己的问题:-)

Yes, it is safe. The using declarations only add the boost functions to the detail namespace. You basically answered your own question :-)

再想一想:即使有人同时使用您的detail命名空间和boost命名空间，for_each等仍然会引用相同的函数，因此别名不会成为问题. 如果这些名称随后与提供for_each的其他库冲突，则仍可以通过在名称空间前添加前缀来消除该函数的用法.但是，如果没有人使用using您的命名空间，您就可以了.

One more thought: Even if somebody were to use your detail namespace and the boost namespace at the same time, for_each etc. would still refer to the same function, so that the alias would not be a problem. If the names then collide with other libraries providing a for_each, you could still disambiguate the usage of the function by prefixing the namespace. But if nobody is usingyour namespace, you are fine.

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