Operator overloading C++

[l0ngb1t]

ok am trying to understand what operator overloading does and why we use it
but am having trouble getting it :S:S:S
can any one explain it to me in an easy way (suck-o style )

[IceDane]

Operator overloading is sometimes useful and sometimes necessary.

Let's say you're going to write a string class of your own.

Code: Select all

class MyString
{
public:
    MyString(char* str)
    {
          theString_ = new char[strlen(str) + 1];
          strcpy(theString_, str);
     }
private:
    char* theString_;
};

Some people would definitely want to do something like:

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MyString lol("cake");
MyString wat = lol;

Now, C++ will create an assignment operator for you if you don't provide one yourself, by simply doing member-to-member assignment. Seeing as your string is contained in an array(pointed to by a pointer), this means that if you do the above without overloading the assignment operator, this will happen:

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MyString lol("cake");
// lol.theString_ contains some address like 0x100
// Now wat = lol, and the default assignment operator
// simply does:
// wat.theString_ = lol.theString_
MyString wat = lol;
// Assuming we can do lol[index] on our string, and we want to modify
// one of the strings, like this:
lol[0] = 'W';
// We are directly modifying the string at address 0x100, which means that
// Both strings get modified

So, because the default assignment operator simply copies the address, we're modifying both strings at the same time - they both contain a pointer to the same string.
We can solve this by writing our own assignment operator, that copies the string into new memory.
This goes inside our class, in public:

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MyString& operator=(const MyString& rhs)
{
     // Note that we have access to all of rhs's members, regardless of 
     // Their access modifiers.
     theString_ = new char [strlen(rhs.theString_) + 1];
     strcpy(theString_, rhs.theString_);
}

And now we can modify the individual strings without modifying both of them.

There are many other uses for operator overloading -- as an example, or an exercise, you could try implementing a simple string class of your own, where you also overload the + and += operators to concatenate strings together.

If this wasn't what you were looking for, please be a bit more specific about what you want to know.

[l0ngb1t]

ok thank you ...
way much clearer
i appreciate it mate ...