26用d编程接口

interface SoundEmitter {
    // ...
}
interface SoundEmitter {
    string emitSound();    //仅声明
}
interface I {
    int func(int i)
    in {

    } out {    //可用进出来保证
    }
}
class Violin : SoundEmitter {
    string emitSound() {
        return "sss";
    }
}

class Bell : SoundEmitter {
    string emitSound() {
        return "ding";
    }
}
void useSoundEmittingObject(SoundEmitter object) {
    //接口实现多态
    writeln(object.emitSound());
}
interface CommunicationDevice {
    void talk(string message);
    string listen();
}//多个接口
class Phone : SoundEmitter, CommunicationDevice {
    // ...
}
class Phone : SoundEmitter, CommunicationDevice {
    string emitSound() {           // for SoundEmitter
        return "rrring";
    }

    void talk(string message) {    // for CommunicationDevice
        // ... put the message on the line ...
    }

    string listen() {              // for CommunicationDevice
        string soundOnTheLine;
        // 处理
        return soundOnTheLine;
    }
}
class Clock {
    // ... clock implementation ...
}

class AlarmClock : Clock, SoundEmitter {
//可继承一个类,多个接口
    string emitSound() {
        return "beep";
    }
}
    static size_t makeNewId() {
        immutable newId = nextId;
        ++nextId;
        return newId;
    }
//静态成员,只能包含静态变量.不能含`成员变量`,没有`本`.

final表最终函数,表最终类(叶类)