如何绑定，存储和执行std :: function对象？

Question

I want to bind a function with arguments, store it in a queue and execute it later. The code so far:

struct Foo {
    ...
    void some_function(int);
    ...
};


Foo:another_function(){ 
     // get the instance of bar
     Bar* bar = Environment->getBar();
     // bind the function
     std::function<void<const Foo&, int> func  = 
        std::bind(&Foo::some_function, this, 42);
     // add it to bar
     bar->add(func);
};

The prototype of the queue in class Bar looks like

std::queue<std::function<void<const Foo&, int>> jobs;

However, if I'm going to execute the object stored in queue I get an error about missing arguments. The code for executing stored objects

Bar::worker(){
    std::function<void<const Foo&, int> job:


    {
        ...
        job = jobs.front();
        jobs.pop();
        ...
    }


    job();

} 

So, the error seems pretty clear to me (how should the compiler know that the stored object is actually one with arguments and therefore doesn't need ones), but I don't know how to handle this. I'm also wondering if passing the 'this' to the bind might not cause at a later point of time, eg if the object doesn't exist anymore.

Thanks in advance! Michael

PS: There is already an thread with a similiar topic on that, over here , but it didn't help much

Answer 1

The prototype of some_function is:

void Foo::some_function(int);

Let's examine this expression:

std::bind(&Foo::some_function, this, 42)

What the expression does is create a callable object, let's call it B . When B is called, it will call Foo::some_function , with the arguments bound to this and 42 . Since this binds all of the parameters of Foo::some_function , there are no parameters left for B . Therefore, the function type of B 's invocation is void () .

In other words, your std::function is of the wrong type. jobs should be typed like this:

std::queue<std::function<void()> jobs;

And of course func should be typed as std::function<void()> as well.