如何将对象的方法传递给外部函数 [英] How to pass an object's method to an external function

问题描述

给定一个名为 myObj 的对象，其中包含函数 doThis 和 doThat ，将对象（和指令到函数）传递给外部函数的最好方法是什么？

Given an object named myObj with functions doThis and doThat, what is the best way to pass the object (and the directive to a function) to an external function?

作为我目前做的一个例子，我一个外部函数 void whatToDo（myClass myObj，string myFunction）其中我简单地传递 doThis c $ c> doThat 为 myFunction 并检查：

As an example of how I am currently doing this, I an external function void whatToDo( myClass myObj, string myFunction) where I simply pass in either doThis or doThat as myFunction and check it:

void whatToDo( myClass myObj, string myFunction) {
    if( myFunction == "doThis") myObj.doThis();
    if( myFunction == "doThat") myObj.doThat();
}

但是，随着类的增长，这变成一个更糟的选择。有没有办法将实际的函数传递给 whatToDo ，以便我可以直接调用它？

However, as the class grows, this becomes a worse and worse option. Is there a way to pass the actual function to whatToDo so that I can just call it directly?

推荐答案

这是成员函数的指针：

void whatToDo(myClass& myObj, void (myClass::*p)())
{
    // p is a pointer to a member function class myClass that
    // takes no arguments and returns void

    // you can invoke it thusly
    (myObj.*p)();
}

您可以提供以下指针：

struct myClass {
    void doThis();
    void doThat();
};

myClass c;
whatToDo(c, &myClass::doThis); // will invoke c.doThis();
whatToDo(c, &myClass::doThat); // will invoke c.doThat();

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