c 2b 2b callback function

1class Foo {
2	int (*func)(int);
3  
4public:
5  	void setCallback( int (*cFunc)(int) ) {
6      func = cFunc;
7    }
8  
9  	void set() {
10    	setCallback(callback);	// Set callback function to be called later
11    }
12  
13    void use() {
14      	func(5);	// Call the previously set callback function
15    }
16          
17  	// Note the 'static'
18    static int callback(int param) {
19      	return 1;
20    }
21};

1//Define a type for the callback signature,
2//it is not necessary, but makes life easier
3
4//Function pointer called CallbackType that takes a float
5//and returns an int
6typedef int (*CallbackType)(float);  
7
8
9void DoWork(CallbackType callback)
10{
11  float variable = 0.0f;
12
13  //Do calculations
14
15  //Call the callback with the variable, and retrieve the
16  //result
17  int result = callback(variable);
18
19  //Do something with the result
20}
21
22int SomeCallback(float variable)
23{
24  int result;
25
26  //Interpret variable
27
28  return result;
29}
30
31int main(int argc, char ** argv)
32{
33  //Pass in SomeCallback to the DoWork
34  DoWork(&SomeCallback);
35}
36

1// C++ callback function
2
3class Base {
4public:
5  void doSomething() {
6    using namespace std::placeholders;
7    // std::placeholders::_1 is for the callback parameter
8    // use _1 for 1 argument
9    // or _1, _2, _3 for 3 arguments and so on
10    something.setCallback(std::bind(&Base::callback, this, _1));
11    // std::bind is needed, otherwise 
12    // the callback function would need to be static
13  }
14  
15  // Callback function
16  void callback(int i) {
17    std::cout << "Callback: " << i << std::endl;
18  }
19}