Operator Overloading ( = )

Question

I'm just a beginner in the C++ language and I have some questions on this piece of code. I am trying to overload some operators.

string& operator = (char R) { string T = R ; *this = T; return *this; }

First Question: Why I need to overload the equal operator while the constructor can do the job?
Second Question: (Not Related) What does (char R) means?

All about operator overloading: http://stackoverflow.com/questions/4421706/operator-overloading — Christian Garbin, Mar 09 '13 at 12:57
it is string T (edited it).. about the C thing.. I know.. It just didn't get removed.. it stuck there dunno why, sorry about that and thanks for the edit :s — geekybedouin, Mar 09 '13 at 13:07

Jason · Accepted Answer · 2013-03-09T13:04:36.200

2

First Question: Why I need to overload the equal operator while the constructor can do the job?

The constructor is designed to "construct" an object ... while there is something called a copy-constructor, it is not designed to actually copy an already existing object into another already existing object of the same (or convertable) type ... that is the job of the operator=. Also you are not "overloading" the operator= method, but rather creating a user-defined version of the method to be used instead of the default compiler-created method for the object type which would simply brute-force copy the bits of the memory footprint of one object into another ... if your object is managing it's own pointers, etc., such a brute-force copy can be a very bad thing as pointer ownership becomes ambiguous, etc.

edited Mar 09 '13 at 13:04

answered Mar 09 '13 at 12:56

Jason

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Got the point.. I forgot that the constructor is only called once.. so because of that we use those user-defined versions for farther edit.. right? – geekybedouin Mar 09 '13 at 13:15
Right, after the constructor is called and the object instance exists, then the assignment operator is used for copies. Keep in mind the ["Rule of Three"](http://en.wikipedia.org/wiki/Rule_of_three_(C%2B%2B_programming)) though ... if you actually need a user-defined assignment operator, then you probably also need a user-defined copy-constructor and destructor for your class since you are most likely managing resources the default compiler versions of those methods will fail to handle correctly. – Jason Mar 10 '13 at 08:26

score 0 · Answer 2 · answered Mar 09 '13 at 12:57

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(char R) is the right-side argument of the operator (here =)

You want to do that so you can set a value after initialization

//constructor
Foo a('f')
//copy constructor
Foo b = Foo('p');
// operator=
b = 'g';

answered Mar 09 '13 at 12:57

drahnr

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score 0 · Answer 3 · answered Mar 09 '13 at 12:57

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(char R) is the argument to the operator just like you have an argument to a normal function.

answered Mar 09 '13 at 12:57

uba

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score 0 · Answer 4 · answered Mar 10 '13 at 15:40

0

Operator overloading in C++ . One of best version here.

http://msumca2012.blogspot.in/2013/03/oop-41-operator-overloading-in-c.html

answered Mar 10 '13 at 15:40

user2130443

1

Welcome to Stack Overflow! Whilst this may theoretically answer the question, [it would be preferable](http://meta.stackexchange.com/q/8259) to include the essential parts of the answer here, and provide the link for reference. – Emil Mar 10 '13 at 16:03

Operator Overloading ( = )

4 Answers4