Classes Implementing Interfaces

Deprecated Feature

Like operations on classes, classes inheriting from interfaces or providing remote operations like interfaces are deprecated as of Ice 3.7. Skip this page unless you need to communicate with old applications that rely on this feature.

A Slice class can also be used as a servant in a server, that is, an instance of a class can be used to provide the behavior for an interface, for example:

Slice

module M
{
    interface Time
    {
        idempotent TimeOfDay getTime();
        idempotent void setTime(TimeOfDay time);
    }

    class Clock implements Time
    {
        TimeOfDay time;
    }
}

The implements keyword indicates that the class Clock provides an implementation of the Time interface. The class can provide data members and operations of its own; in the preceding example, the Clock class stores the current time that is accessed via the Time interface. A class can implement several interfaces, for example:

Slice

interface Time
{
    idempotent TimeOfDay getTime();
    idempotent void setTime(TimeOfDay time);
}

interface Radio
{
    idempotent void setFrequency(long hertz);
    idempotent void setVolume(long dB);
}

class RadioClock implements Time, Radio
{
    TimeOfDay time;
    long hertz;
}

The class RadioClock implements both Time and Radio interfaces.

A class, in addition to implementing an interface, can also extend another class:

Slice

interface Time
{
    idempotent TimeOfDay getTime();
    idempotent void setTime(TimeOfDay time);
}

class Clock implements Time
{
    TimeOfDay time;
}

interface AlarmClock extends Time
{
    idempotent TimeOfDay getAlarmTime();
    idempotent void setAlarmTime(TimeOfDay alarmTime);
}

interface Radio
{
    idempotent void setFrequency(long hertz);
    idempotent void setVolume(long dB);
}

class RadioAlarmClock extends Clock
                      implements AlarmClock, Radio
{
    TimeOfDay alarmTime;
    long hertz;
}

These definitions result in the following inheritance graph:

A Class using implementation and interface inheritance.

For this definition, Radio and AlarmClock are abstract interfaces, and Clock and RadioAlarmClock are concrete classes. As for Java, a class can implement multiple interfaces, but can extend at most one class.

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