how to pass "this" in c++

Question

I'm confused with the this keyword in C++, I'm not sure that if I'm doing the right thing by passing this. Here is the piece of code that I'm struggling with:

ClassA::ClassA( ClassB &b) {      b.doSth(this);     // trying to call b's routine by passing a pointer to itself, should I use "this"? }  ClassB::doSth(ClassA * a) {        //do sth } 

Answer 1

You're using it correctly. The this pointer points to the current object instance.

class helper  { public:      void help(worker *pWorker) {           //TODO do something with pWorker . . .      }       void help2(worker& rWorker) {           //TODO do something with rWorker . . .      } };  class worker  { public:      void dowork() {           //this one takes a worker pointer so we can use the this pointer.           helper.help(this);            //to pass by reference, you need to dereference the this pointer.           helper.help2(*this);      }      helper helper; }; 

Also, say you declare worker *pW = new worker(). If you call one of the methods (dowork) on the pW object, you will notice that the this pointer and pW have the exact same value (they are both the same address).

(haven't tested that to make sure it builds, but I think it should).

Answer 2

In C++, this is a keyword which is defined as "the pointer to the current object instance". So your code above is correct.

Depending on the inheritance/composition relationship between ClassA and ClassB, there are probably better ways to achieve what you are doing than by using the this pointer.