我可以声明“使用命名空间”吗？在 C++ 内部班级？

发布于 2025-01-06 01:36:43 字数 236 浏览 1 评论 0原文

假设有一个 C++ 类。还有一个名称空间应该只在我的类中可见。为此该怎么办？

class SomeClass
{
    using namespace SomeSpace;

public:
    void Method1();
    void Method2();
    void Method3();
};

namespace SomeSpace
{
    /*some code*/
};

原文

Assume having a C++ class. And there's a namespace which should be visible only inside my class. What to do for that?

class SomeClass
{
    using namespace SomeSpace;

public:
    void Method1();
    void Method2();
    void Method3();
};

namespace SomeSpace
{
    /*some code*/
};

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兮颜 2025-01-13 01:36:43

using namespace X; 称为 using 指令，它只能出现在命名空间和函数作用域中，但不能出现在类作用域中。所以你想要做的事情在 C++ 中是不可能的。您能做的最好的事情就是在该类的命名空间范围内编写 using 指令，这可能是不可取的。

但转念一想，分析一下你的话，

假设有一个 C++ 类。并且有一个名称空间应该是
仅在我的班级内可见。为此该怎么办？

我建议类似以下的内容，我不确定这是否是您想要的。

class A
{
public:
    void Method1();
    void Method2();
    void Method3();
 
private:
 
    class B
    {
       //public static functions here, instead of namespace-scope
       // freestanding functions.
       //these functions will be accessible from class A(and its friends, if any) 
       //because B is private to A
    };

};

using namespace X; is called a using directive and it can appear only in namespace and function scope, but not class scope. So what you're trying to do is not possible in C++. The best you could do is write the using directive in the scope of the namespace of that class, which may not be desirable.

On second thought, though, analyzing your words,

Assume having a C++ class. And there's a namespace which should be
visible only inside my class. What to do for that?

I'd suggest something like the following, which I am not sure is what you want.

class A
{
public:
    void Method1();
    void Method2();
    void Method3();
 
private:
 
    class B
    {
       //public static functions here, instead of namespace-scope
       // freestanding functions.
       //these functions will be accessible from class A(and its friends, if any) 
       //because B is private to A
    };

};

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梦里的微风 2025-01-13 01:36:43

不，但你可以这样做：

namespace SomeSpace
{
    /*some code*/
};

using namespace SomeSpace;

class SomeClass
{

public:
    void Method1();
    void Method2();
    void Method3();
};

尽管不建议在头文件中应用 using 命名空间指令，并且通常被认为是一种不好的风格。可以放入类的源文件（.cpp）中。

No but you can do it like that:

namespace SomeSpace
{
    /*some code*/
};

using namespace SomeSpace;

class SomeClass
{

public:
    void Method1();
    void Method2();
    void Method3();
};

Though it is not recommended either to apply the using namespace directive in header files and often considered as a bad style. It is OK to put in in a source file (.cpp) of your class.

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