c++ - 如何以及何时正确使用 *this 指针和参数匹配？

Question

当我通过同事编写的代码时，在某个地方，他们使用：

this->doSomething(); //-->case A
doSomething(); //-->case B

事实上，我不确定 *this 指针的用途... :(

另一个与参数匹配的问题：

obj.doOperation();  //-->case C
(&obj)->doOperation(); //-->case D

事实上，这两种情况都在执行所需的操作，这仅仅是让代码看起来更复杂的一种方法吗？

您对以上两个问题有何建议？什么时候使用它们合适，为什么？

Answer 1

这不是您问题的答案，但请注意两个片段可能会做不同的事情：

namespace B { void doSomething() {} }

struct A {    
    void f()
    {
        using B::doSomething;
        this->doSomething(); // call A::doSomething
        doSomething(); // calls B::doSomething
    }

    int a;
    void g(int a)
    {
        this->a = a; // assigns argument to member
    }

    A* operator & () { return this; }
    void doOperation() {}
    void doSomething() {}
};

void g(A &obj)
{
    obj.doOperation();  // calls A::doOperation directly
    (&obj)->doOperation(); // calls A::operator & first
}

Answer 2

Cases B and C are always the appropriate way. Cases A and D are equivalent and do nothing different.

A few exceptions to that:

• If the class has an overloaded operator& that does surprising things, then case D could do something different that C. Actually having classes which do this is not recommended, since it would be confusing.
• If there is a local variable doSomething (or something else of that name in the local scope), then A would refer to a different doSomething than B. Again it isn't recommended to get yourself into such a situation, better give different names to different things.

Answer 3

C 和 D 不同。如果是虚拟的，case D 将执行虚拟调用，如果不是引用doOperation，case C 将执行非虚拟调用。obj然而，这假设operator&并且operator->没有被重载。

我倾向于使用 A 而不是 B，因为可能有一个本地doSomething标识符。在模板代码内部，情况可能会变得更糟（尽管我现在无法提供精确的示例）。这是一个好习惯。