Member Functions

Because string is a library or class type, it also has methods, just like the Java String class has methods such as length(), toUpper() and charAt(). In C++ instead of calling these methods, we use the term member function instead. Let's look at the difference between a regular (or "free") function in C++, and a member function.

In the string class, you've already seen the getline() function. The prototype for getline() looks like this:

istream& getline(istream& in, string& str);

The function has two parameters: the input stream to read from, and the string object to modify; it returns a reference to its input stream (which may be ignored).

string line;
getline(cin, line);

Although getline() is declared inside the <string> header, it is not part of the string class; it is just a regular function. Member functions, in contrast, are part of a class, and, as in Java, they are called by using a special syntax:

receiver.request(arguments);

In this case, receiver is an object, and request is a member function defined in that class. When compiled, the address of the receiver object is passed to the member function as an invisible or implicit first parameter. Inside the member function, that implicit parameter is accessed using the keyword this, in a manner similar to Java.

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