Abstraction

Interfaces and abstraction

Interfaces help make parts of programs independent from each other. This is called abstraction. For example, a program that deals with musical instruments can be written primarily by using the MusicalInstrument interface, without ever specifying the actual types of the musical instruments.

A Musician class can contain a MusicalInstrument without ever knowing the actual type of the instrument:

class Musician {
    MusicalInstrument instrument;
    // ...
}

Different types of musical instruments can be combined in a collection without regard to the actual types of these instruments:

MusicalInstrument[] orchestraInstruments;

Most of the functions of the program can be written only by using this interface:

bool needsTuning(MusicalInstrument instrument) {
    bool result;
    // ...
    return result;
}
void playInTune(MusicalInstrument instrument) {
    if (needsTuning(instrument)) {
        instrument.adjustTuning(); 
    }

    writeln(instrument.emitSound()); 
}

Abstracting away parts of a program from each other allows making changes in one part of the program without needing to modify the other parts. When implementations of certain parts of the program are behind a particular interface, the code that uses only that interface does not get affected.

---