I overloaded the << operator of a class. How do I have to overload the operator if I want to use it on pointers, like the following?
class A {
std::string operator<<(std::string&);
}
aInst << "This works";
aPointer << "This doesnt work";
aPointer->operator<<("Whereas this works but is useless");
I hope you can help me.
heinrich
You need to dereference the pointer first.
A *ptr = new A();
(*ptr) << "Something";
The only other way is the way you described above
Edit: Andre's solution below is workable as well, but like he said it may not be a good idea.
First off, to stick with standard conventions, your operator<< should be declared like this:
class A {
A& operator<<(const std::string&);
};
Now, technically, you could achiever part of what you want by implementing the following global function:
A * operator<< ( A * a, const std::string& s ) { (*a) << s; return a; }
This would allow statements such as:
string s = "this will be printed."; aPointer << s;
aPointer << string("this will be printed");
However, you won't be able to write the following:
aPointer << "this will not compile.";
In any case, writing such an operator would be confusing, at best. You should live with the more simple syntax of
(*aPointer) << "this will be printed.";
and write code that sticks to established conventions to allow others (and yourself, in a few weeks) to read your code.
You cannot do that. Operator functions are only considered for operands that have enumeration or class types among them.
You after all shift a pointer, but not a class. You need to explicitly say that you want to shift into a class object by dereferencing the pointer first.
Normally there is no good reason doing that, because semantically operator << return reference to stream object. And technically you basically can't do that.
operator<< should return the left-hand side argument.