在成员函数中返回* this [英] Returning *this in member functions

问题描述

我最近使用了一个允许使用以下类型语法的库：

I recently used a library that allows the following type of syntax:

MyClass myObject;
myObject
    .setMember1("string value")
    .setMember2(4.0f)
    .setMember3(-1);

显然，这是通过让setter返回MyClass&类型;例如return * this。我喜欢这种代码的外观，但我看不到很多。当这种情况发生时，我通常怀疑为什么。

Obviously this is accomplished by having the setters return a MyClass & type; something like return *this. I like the way this code looks, but I don't see it a lot. When that happens I'm usually suspicious as to why.

那么，这是一个坏的做法吗？

So, is this a bad practice? What are some of the implications of doing it like this?

推荐答案

这有时被称为命名参数惯用法或方法链接。这不是坏的做法，它可以帮助可读性。考虑这个例子从C ++常见问题解答

This is sometimes referred to as the Named Parameter Idiom or method chaining. This isn't bad practice, it can aid readability. Consider this example lifted from the C++ FAQ

File f = OpenFile("foo.txt")
            .readonly()
            .createIfNotExist()
            .appendWhenWriting()
            .blockSize(1024)
            .unbuffered()
            .exclusiveAccess();

另一种方法是使用OpenFile方法的位置参数，要求程序员记住每个参数。

The alternative would be to use positional arguments to the OpenFile method, requiring the programmer to remember the position of each argument.

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