Operator overloading

[rliq]

Say I wanted to override the '+' operator for the following class:


public class MyClass
{
private MyType _mySecretInternalRepresentation; // MyType maybe UInt32 for example

public static MyClass operator+(MyClass a, MyClass b)
{
// code required here
}
}

Ok, *I*know how to add a to b, but how can i get at their internal representation so I can perform the add, without exposing the internal representation (making it public) to everyone and breaking one of the fundamental laws of OO ?

Am I missing something? I'm sure in C++ I had access to private members of the *same* class within an operator overload function.

Microsoft give an example in the documentation (see operator overloading C# vs Java) for complex numbers, but their ComplexNumber class has public members which is not good because individual parts of the complex number can be modified independently by external code.

[rliq]

Sorted....

If the operator+ function is NOT static, then you do get access to the parameters private members:

public class MyClass
{
private MyType _mySecretInternalRepresentation; // MyType maybe UInt32 for example

public MyClass operator+(MyClass other)
{
other._mySecretInternalRepresentation; // can access here
}
}

[Mutant_Fruit]

Sorted....

If the operator+ function is NOT static, then you do get access to the parameters private members:

public class MyClass
{
private MyType _mySecretInternalRepresentation; // MyType maybe UInt32 for example

public MyClass operator+(MyClass other)
{
other._mySecretInternalRepresentation; // can access here
}
}
Did you try compiling that? It doesn't compile, the operator overload must be static.



Ok, *I*know how to add a to b, but how can i get at their internal representation so I can perform the add, without exposing the internal representation (making it public) to everyone and breaking one of the fundamental laws of OO ?

You should have just tried rather than asking ;) It works exactly the way you'd expect it to:


public class MyClass
{
private int value; // MyType maybe UInt32 for example

public static MyClass operator +(MyClass left, MyClass right)
{
return new MyClass { value = left.value + right.value };
}
}

[darwen]

As you've found out the operator+ method is a member of the class (even though it's static) so it has access to the private data of instances of the same class.

C# doesn't support instance-level operating overloading (it's not C++). The correct way of overloading an operator is to use a static method as you have done.

Darwen.