CODEWITHSUNDEEP
c++functionpointersreference
ghostrider
ghostrider

Reputation: 5259

passing arguments via reference and pointer C++

I am looking at a code snippet and I have this sequence.

class MyVariable {
....
    CustomType z;
....
}

A.cpp

calling a function f ( & myVariable)

In an included file I do have this :

B.h

void f ( MyVariable * myVariable);

B.cpp

f( MyVariable * myVariable){
   CustomType & x = myVariable ->g();
}

where g is a method of the class MyVariable and the implementation is is :

CustomType & g() {
   ...
    return z; //where you can find z in the class
}

It looks pretty complicated to me though, so my question is :

Does any change to x being reflected to the myVariable that is used as a parameter in the function call in A.cpp?

In other words, if in B.cpp, I do something like this :

// change x with some value

Will that change be reflected in the myVariable as well?

Upvotes: 0

Views: 72

Answers (4)

Vikram
Vikram

Reputation: 76

Whenever the variable is passed either by reference or by address, any change to that variable in called function are reflected in caller function. To answer your question, Yes any change to X will be reflected to myVariable and that applies even if X is private variable.

Upvotes: 0

Sourav Kanta
Sourav Kanta

Reputation: 2757

Yes as the variables address is passed any change of x within the function changes the value of the variable with which function is called.Both the of the pointers refer to the same memory location.So change in the value of one changes the others value automatically.

Upvotes: 1

Arkanosis
Arkanosis

Reputation: 2334

Yes. There's no copy anywhere as you're either using pointers or references when you “pass” the variable from one place to another, so you're actually using the same variable everywhere.

In g(), you return a reference to z, then in f() you keep this reference to z. Moreover, when you call f(), you don't even copy myVariable, but its address (in the form of a pointer), so you'll actually modify the z member of the myVariable variable you have in A.cpp.

Upvotes: 1

TartanLlama
TartanLlama

Reputation: 65600

x is a non-const reference to the z member of myVariable, so yes, if you change x, myVariable->z will change as well.

You can think of references as aliases, x is just another name for myVariable->z.

Upvotes: 1

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