Advanced Programming Techniques in D/

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Superclass Members

Superclass Members

Get to learn how to access and construct superclass members.

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Accessing superclass members

The super keyword allows referring to members that are inherited from the superclass.

D
class Clock {
    int hour;
    int minute;
    int second;
    void adjust(int hour, int minute, int second = 0) { 
        this.hour = hour;
        this.minute = minute;
        this.second = second;
    } 
}
class AlarmClock : Clock {
    int alarmHour;
    int alarmMinute;
    
    void adjustAlarm(int hour, int minute) { 
        alarmHour = hour;
        alarmMinute = minute; 
    }
    void foo() {
        super.minute = 10; // The inherited 'minute' member
        minute = 10; // Same thing if there is no ambiguity 
    }
}
void main() {}

The super keyword is not always necessary; minute alone has the same meaning in the code above (line # 23). The super keyword is needed when both the superclass and the subclass have members under the same names.

If multiple classes in an inheritance tree define a symbol with the same name, one can use the specific name of the class in the inheritance tree to disambiguate between the symbols:

D
import std.stdio;



class Device {

    string manufacturer;

}



class Clock : Device {

    string manufacturer;

}



class AlarmClock : Clock { 

    // ...



    void foo() {

        Device.manufacturer = "Sunny Horology, Inc.";

        Clock.manufacturer = "Better Watches, Ltd."; 

    }

}



void main() {

    auto alarmC = new AlarmClock();

    alarmC.foo();

    writeln(alarmC.manufacturer);

}
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