pimpl成语与桥梁设计模式 [英] pimpl idiom vs. bridge design pattern

问题描述

我只是注意到一个新的术语pimpl成语，这个成语和桥梁设计模式有什么区别？我很困惑。

I just noticed a new term pimpl idiom, what's the difference between this idiom with Bridge design pattern? I am confused about that.

我也注意到pimpl成语总是用于交换功能，这是什么？

I also noticed the pimpl idiom is always used for swap function, what's that? Could anybody give me an example?

推荐答案

PIMPL是隐藏实现的一种方式，主要是打破编译依赖。

PIMPL is a way of hiding the implementation, primarily to break compilation dependencies.

另一方面，Bridge模式是一种支持多种实现的方式。

The Bridge pattern, on the other hand, is a way of supporting multiple implementations.

swap 是一个用于交换两个对象的值的标准C ++函数。如果你将指针交换到不同实现的实现，你基本上是在运行时改变类的机制。

swap is a standard C++ function for exchanging the values of two objects. If you swap the pointer to the implementation for a different implementation, you are essentially changing the mechanism of the class at runtime.

但是在它的基本和通用形式，使用PIMPL指向单个实现，因此没有具有不同子类的抽象类 - 只有一个类，向前声明，并在别处编译。更改实现类不需要对包含主头文件的源文件进行重新编译。

But in its basic and common form, a class using PIMPL points to a single implementation, so there is no abstract class with distinct subclasses — just one class, forward declared, and compiled elsewhere. Changing the implementation class does not require any recompilation of sources that include the main header.

例如，假设你有很多私有成员函数，私有枚举和私有数据。随着类的开发和维护，这些私有的位变化相当频繁。如果 #include 依赖性是这样的，接触这个头文件导致大量的源被重新编译，你有一个很好的候选人PIMPL。

For example, say you have a lot of private member functions, private enums, and private data. And these private "bits" change fairly frequently as the class is developed and maintained. If the #include dependencies are such that touching this header file causes a large number of sources to be recompiled, you have a good candidate for PIMPL.

所以Bridge模式是面向对象设计，而PIMPL模式是关于文件的物理设计。

（有关物理设计的更多信息，我推荐John Lakos着作的大型C ++软件设计一书。）

(For more on physical design, I recommend the book Large-Scale C++ Software Design by John Lakos.)

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