How to interpret "operator const char*()" in operator overloading?

Question

I was looking at one of the implementation of String class and noticed the following overloaded == operator.

String f = "something";
String g = "somethingelse";
if (f == g)
    cout << "Strings are equal." << endl;

bool operator==(String sString)
{
    return strcmp(operator const char*(), (const char*)sString) == 0; 
}

I understood most of the part except operator const char*() what exactly its been used for? I have very basic knowledge of operator overloading , can someone please throw some more light on this?

Answer 1

It is an explicit call to the operator const char*() member function. This code would do the same:

return strcmp(static_cast<const char*>(*this), (const char*)sString) == 0;

But there are more than one thing wrong with that code:

1. it should not use C-cast, but C++-casts (e.g. static_cast) for the right argument
2. operator== should be a free function, not a member function
3. A string class should normally not have an operator const char*
4. If the String class is implemented reasonably, the operator== should take both parameters as const references