Returning *This

[Analyzer]

Why would you ever return a *this pointer in a memeber function of a class?

for example:

Time::Time( int hr, int min, int sec ){
setTime( hr, min, sec );
}

Time &Time::setTime(int h, int m, int s){

setHour(h);
setMinute(m);
setSecond(s);
return *this; //What is it returning??? I know its returning the OBJECT but why?
}

Why is it returning the Object?? And in the constructor "setTime" is called but there are no variables to retrieve the returning value?? so why is it returning *this..

also why does it do this Time &Time::setTime isn't this saying that its going to return a reference even though it doesnt return a reference it returns a pointer.. and can't the code be return as
Time::& setTime??

I know I got alot of questions.

[ne555]

That will allow you to do

Time t,u,v,w;
t.setTime(h,m,s).setAnotherThing(a,b,c); // you are modifying the same object 
u = v = w = Time(h,m,s);
u = v.setTime(h,m,s) = w;

this is a pointer to the object, so *this is an object.
However that concatenation of methods can be confusing. In setters I prefer not returning anything (throwing an exception or setting error flags), or return bool

[Analyzer]

Yes but when its returning the Object.. what does it return to??

Like when the object is returned where does it go???

[Athar]

It returns a reference to the object - that is, an alias to itself.
If you don't "use" it, nothing happens.

[Analyzer]

I understand, how in Operator overloading you might need to return a *this (or ojbect)

like as in

operator&>(const otherclass &otherobject){

return otherobject < *this
}

but in the

Time::Time( int hr, int min, int sec ){
setTime( hr, min, sec );
}

Time &Time::setTime(int h, int m, int s){

setHour(h);
setMinute(m);
setSecond(s);
return *this; //What is it returning??? I know its returning the OBJECT but why?
}

What is the point of returning the Object?? How does it allow for concading???

[Athar]

Well. Consider:

Time someTime(3,13,37);
//Now we call setTime:
someTime.setTime(6,27,14);
//Since setTime returns a reference to the object, the above can be used as an alias to someTime, e.g.
someTime.setTime(6,27,14).setTime(3,13,37).setTime(12,54,28); //not very useful, but possible
//and:
Time someOtherTime=someTime.setTime(6,27,14); //set someTime, then construct someOtherTime from someTime 

Having setTime return a reference to the object is not particularly useful, however it is useful for operator=.

[Analyzer]

Yes its now very clear to me. Thanks for your help.

[teapotz]

........ =.=
hihi
Pardon me for asking..
i tried to read for a few times... i dun even know what eu all are talking abt...
and for Analyzer said its clear ....

I feel so dumb now....