this is one "classy" thread

This is a discussion on this is one "classy" thread within the C++ Programming forums, part of the General Programming Boards category; ok, so the title is a bad joke, anyways i am reading a tutorial on classes and well here's what ...

  1. #1
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    this is one "classy" thread

    ok, so the title is a bad joke, anyways i am reading a tutorial on classes and well here's what it says
    every object has a special pointer call "this", which refers to the object itself. So the members of the Dog class can be referred to as this->age or this->weight, as well as, age or weight. If there is no ambiguity, no qualification is required. So in the getWeight method, "weight" can be used instead of "this->weight". In the setWeight method an ambiguity exists. Since the parameter passed is "weight" and there is a class member "weight", the "this" pointer must be used. Finally, a note about syntax. If "this" is a pointer to a class, then the member selection operator, "->", can be used to access the contents of its members.
    the tutorial is here and i was wondering whats up with the this-> pointer?

    edit: i wasn'tvery clear before, i want to know why i would need this-> in my code?
    Last edited by sreetvert83; 09-09-2005 at 08:55 PM. Reason: not clear
    If a mime dies in the woods and no one is around to hear it, does it make a sound?

  2. #2
    Dae
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    If you have two variables, one from a parameter, and one from a class, then to access the class one you'd use this->. I don't know how that wouldnt cause an error, or why a programmer would do that, so I dont find the advice useful.

    Most of the time I use 'this' in operator overloading, because you are taking 2 objects (usually), the one you are editing, and the one a reference is passed to (ie. ThisObject = ThisObject + AnotherObject). The AnotherObject would have a reference passed to the operator+, of the object ThisObject, and the operator+ would return it so itd be ThisObject = _______, so what do you want it to equal? You are altering in ThisObjects operator+, and therefor probably altering ThisObject, so how do you return the class you're processing in if you dont have a reference passed of it or anything? 'this'. Which results in ThisObject = ThisObject (but after the processing, adding of ThisObject and AnotherObject). Its used like return this; in this case, although it could be return this->total; but of course I said I dont see the point of that, just return total; if you need ot.

    Think of the class, basicly it can access the object of itself without needing to create it (ThisClass ThisObject) and of course it contains the data of the object (not a blank one). Then it can do what it wants with the object of itself, like send it as a parameter, return the object, maybe create a copy and change it, then set the original this to that copy - all inside the class declaration itself (not to an object of it in say main).
    Warning: Have doubt in anything I post.

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    wow, i have no idea what you just said, i think you said that the this-> isn't neded in this case, and i can just return the variables?
    If a mime dies in the woods and no one is around to hear it, does it make a sound?

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    If, in a class method, you have local variables with the same name as member variables, you can use this-> to specify that you want to use the member variables. Otherwise the local variables will be used. A better solution might be to just give your variables unique names.

    There are other uses of the this pointer that are slightly more advanced.

  5. #5
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    Code:
    class c {
    private:
        int i;
    public:
        c() : i(5) {}
    
        void print() {
            int i = 3;
            cout << i << endl;
            cout << this->i << endl;
        }
    };
    
    int main() {
        c var;
    
        var.print();
        return 0;
    }
    That should print
    Code:
    5
    3
    dwk

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