宏和函数中的"this"指针 [英] 'this' pointer in macro and function

问题描述

我有一些代码，该代码使用调用此代码的类的"this"指针.例如:

I have some code which use 'this' pointer of class which calls this code. For example:

Some::staticFunction<templateType>(bind(FuncPointer, this, _1));

这是我从boost调用bind函数.但这没关系.现在，我必须包装此代码.我做了一个宏:

Here is I'm calling bind function from boost. But it doesn't matter. Now I have to wrap this code. I made a macro:

#define DO(Type, Func) Some::staticFunction<Type>(bind(FuncPointer, this, _1));

然后编译器将此代码插入到调用此宏的类中，因此"this"取自调用者.但是我不想使用宏并且更喜欢函数(内联).但是如何解决这个"过去.我可以在宏等内联函数中使用它，还是必须手动传递它?

And compiler insert this code into class which calls this macro, so 'this' takes from caller. But I don't want to use macro and prefer function (inline). But how to resolve 'this' passing. Could I use it in inline function like in macro or I have to pass it manually?

推荐答案

this关键字可以由您调用的函数放置

The this keyword can be put by the function you call

class MyClass {
  // ...
  template<typename Type, typename Func>
  void doit(Func f) {
    Some::staticFunction<Type>(bind(f, this, _1));
  }
};

之后您可以致电

doit<templateType>(FuncPointer);

---

如果愿意，您可以继承该功能

---

If you like you can inherit the function

// T must be a derived class of MyRegister<T>
template<typename T>
class MyRegister {
protected:
  template<typename Type, typename Func>
  void doit(Func f) {
    Some::staticFunction<Type>(bind(f, (T*)this, _1));
  }
};

class MyClass : MyRegister<MyClass> {
  // ...
};

这样，您就可以只使用doit而不是先编写它，就像使用宏一样.如果您在其中使用函数的种类很多，则很有用.

That way you can just use doit and not first write it, just like with the macro. Useful if you have a wide range of classes that you use the function in.

注意，由于私有继承，此处C-Style强制转换是必需的(不能使用static_cast).如果T是从MyRegister<T>

Notice that the C-Style cast is required here (can't use static_cast), because of the private inheritance. It's a safe cast if T is derived from MyRegister<T>

就个人而言，我更喜欢此宏.请注意，您的宏无法处理类型名称中的逗号

Personally i would prefer this over the macro. Notice that your macro can't cope with commas in the type-name

DO(std::pair<A, B>, g);

这尝试将3个参数传递给宏而不是2.您可以颠倒类型和函数的顺序，并使用可变参数宏(这是C ++ 0x功能，但在C ++的某些编译器中可用) 03模式)，也可以使用typedef并传递别名.

This tries to pass 3 arguments to the macro instead of 2. You could reverse the order of the type and the function and use variadic macros (which are a C++0x feature, but available in some compiler in C++03 mode) or you could use a typedef and pass the alias name.

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