使用d指针的优点和缺点是什么？ [英] What are the pros and cons of using d-pointers?

问题描述

d指针在Qt中被大量使用，它们是pimpl成语的实现。我知道pimpl成语的优点和缺点。但我错过了d指针实现的优势。 这里和这里是d指针的示例。
不是更容易使用这个吗？

d-pointers are heavily used in Qt, they are an implementation of pimpl idiom. I know advantages and disadvantages of pimpl idiom. But I have missed the advantages of d-pointers implementation. Here and here are the samples of d-pointers. Isn't it easier to just use this?

class MyClassPrivate;
class MyClass {
  // interface methods
private:
  MyClassPrivate *pimpl_;
};

推荐答案

d指针模式的宏集提供了一些排序方便和一致性。例如，Q_DECLARE_PRIVATE确保Foo的pimpl私有类被命名为FooPrivate，FooPrivate结束Foo，并创建一个很好的内联函数（const和nonconst版本），称为d_func（）。后者用于Q_D宏，基本上创建一个指向私有类实例的作用域/局部变量d。

The set of macros for d-pointer pattern provides some sort convenience and consistencies. For example, Q_DECLARE_PRIVATE ensures that the pimpl private class for Foo is named as FooPrivate, that FooPrivate befriends Foo, and creates an nice inline function (both const and nonconst versions) called d_func(). The latter is used in Q_D macro, which basically creates a scoped/local variable d which points to the private class instance.

简而言之，您不需要使用Q_DECLARE_PRIVATE和其他宏，但这样做会使代码更短，更清晰，更一致。

In short, you need not use Q_DECLARE_PRIVATE and other macros, but doing so will make the code shorter, cleaner, and consistent.

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