C ++：将函数分配给tr1 :: function对象 [英] C++: Assigning a function to a tr1::function object

问题描述

我们的一个类提供了tr1 :: function回调对象。

One of our classes provides tr1::function callback object. When I try assigning a member function to it, though, I get a compiler error.

下面的例子是未经测试的，只是为了说明：

The examples below are untested and just to illustrate:

Foo.h：

class Foo()
{
public:
  Foo();
  std::tr1::function<void (int x)> F;
}

Bar.h：

class Bar()
{
public:
   Bar();
   Foo* foo;
   void HookUpToFoo();
   void Respond(int x);
}

Bar.cpp：

Bar()
{
    this->foo = new Foo();
    this->HookUpToFoo();
}

void Bar::HookUpToFoo()
{
  this->foo->F = &Bar::Respond; // error
}

void Bar::Respond(int x)
{
       // do stuff
}

我们得到的编译器错误指的是xrefwrap中的一行，并且是
错误1错误C2296：'。*'：illegal ，左操作数具有类型'int'C：\Program Files\Microsoft Visual Studio 9.0 \VC\include\xrefwrap 64

The compiler error we get refers to a line in xrefwrap and is Error 1 error C2296: '.*' : illegal, left operand has type 'int' C:\Program Files\Microsoft Visual Studio 9.0\VC\include\xrefwrap 64

..我是什么在分配一个委托做错了？我想去更现代的路线，并使用tr1 ::函数，而不是函数指针。

..What am I doing wrong in assigning a delegate? I want to go the more modern route and use tr1::function rather than function pointers.

推荐答案

隐藏参数： this 。这使得它与您只接受一个参数的函数对象不兼容。您可以使用 tr1 ：

A member function accepts an additional hidden parameter: this. This makes it incompatible with your function object which only accepts one parameter. You can bind a member function to a particular instance using bind, which is also available in tr1:

using namespace std::tr1::placeholders;

this->foo->F = std::tr1::bind(&Bar::Respond, this, _1);

这将确保 Bar :: Respond 被正确的值绑定到 this 。 _1 是附加参数（ x ）的占位符。

This ensures that Bar::Respond will be called with the correct value bound to this. The _1 is a placeholder for the additional parameter (x).

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