在内联命名空间标题中隐藏私有常量 [英] Hiding private constants in an inline namespace header

问题描述

我有一些内联函数包含在头文件中的命名空间中，目前不能将它们移动到cpp文件中。这些内联函数中的一些使用魔术常量，例如：

I have some inline functions contained within a namespace in a header file and am not currently in a position to move them into a cpp file. Some of these inline functions use magic constants, for example:

// Foo.h
namespace Foo
{
    const int BAR = 1234;

    inline void someFunc()
    {
        // Do something with BAR
    }
}

但是，我想让这些魔法常量私有 - 任何想法如何？我的第一个想法是使用匿名命名空间，因此：

However, I want to make these magic constants private - any ideas how? My first thought was to use an anonymous namespace thus:

// Foo.h
namespace Foo
{
    namespace
    {
        // 'private' constants here
        const int BAR = 1234;
    }

    inline void someFunc()
    {
        // Do something with BAR
    }
}

但是，这不起作用， Foo :: BAR 任何包含 Foo.h 的cpp文件？有没有办法这样做而不创建一个实现cpp文件？

However, this doesn't work and Foo::BAR is available to any cpp file that includes Foo.h? Is there a way to do this without creating an implementation cpp file?

推荐答案

匿名命名空间工作的翻译

您可以考虑将它们移动到详细命名空间中，以向用户表示他们是内部细节：

You can't, anonymous namespaces work for the translation unit they are defined in (or included into in your case).
You could consider moving them into a detail namespace to signal to the user that they are internal details:

namespace foo {
    namespace detail {
        int magic = 42;
    }

    // ... use detail::magic
}

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