C ++中的内部typedefs - 好的风格还是坏的风格？ [英] Internal typedefs in C++ - good style or bad style?

问题描述

我发现自己最近经常做的事是声明typedef与该类中的特定类相关，即

Something I have found myself doing often lately is declaring typedefs relevant to a particular class inside that class, i.e.

class Lorem
{
    typedef boost::shared_ptr<Lorem> ptr;
    typedef std::vector<Lorem::ptr>  vector;

//
// ...
//
};

这些类型在代码中的其他位置使用：

These types are then used elsewhere in the code:

Lorem::vector lorems;
Lorem::ptr    lorem( new Lorem() );

lorems.push_back( lorem );

我喜欢的原因：

• 它减少类模板引入的噪声， std :: vector< Lorem> 变成 Lorem :: vector 等。


• 它作为意图声明 - 在上面的示例中，Lorem类旨在通过 boost :: shared_ptr 并存储在向量中。


• 它允许实现更改 - 即如果Lorem需要更改为intrusively引用计数


• 我认为它看起来更漂亮，可以说更容易一些

• It reduces the noise introduced by the class templates, std::vector<Lorem> becomes Lorem::vector, etc.
• It serves as a statement of intent - in the example above, the Lorem class is intended to be reference counted via boost::shared_ptr and stored in a vector.
• It allows the implementation to change - i.e. if Lorem needed to be changed to be intrusively reference counted (via boost::intrusive_ptr) at a later stage then this would have minimal impact to the code.
• I think it looks 'prettier' and is arguably easier to read.

我不喜欢的原因：

• 有些依赖关系的问题 - 如果你想在另一个类中嵌入一个 Lorem :: vector ，但只需要向前声明Lorem（而不是引入一个依赖于其头文件），那么你最终不得不使用显式类型（例如 boost :: shared_ptr< Lorem> 而不是 Lorem :: ptr ），这有点不一致。 >
  
• 这可能不是很常见，因此更难理解？

• There are sometimes issues with dependencies - if you want to embed, say, a Lorem::vector within another class but only need (or want) to forward declare Lorem (as opposed to introducing a dependency on its header file) then you end up having to use the explicit types (e.g. boost::shared_ptr<Lorem> rather than Lorem::ptr), which is a little inconsistent.
• It may not be very common, and hence harder to understand?

我的编码风格，所以它会是好的，以获得一些其他意见，所以我可以剖析我的想法一点点。

I try to be objective with my coding style, so it would be good to get some other opinions on it so I can dissect my thinking a little bit.

推荐答案

我认为它是优秀的风格，我自己使用它。最好尽可能地限制名称的范围，并且使用类是在C ++中执行此操作的最佳方法。例如，C ++标准库大量使用类中的typedef。

I think it is excellent style, and I use it myself. It is always best to limit the scope of names as much as possible, and use of classes is the best way to do this in C++. For example, the C++ Standard library makes heavy use of typedefs within classes.

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