迭代器模式

  • 迭代器模式Iterator Pattern提供了一种方法顺序访问一个聚合对象中的各个元素，而又无需暴露该对象的内部实现
  • 这样既可以做到不暴露集合的内部结构，又可让外部代码透明地访问集合内部的数据，迭代器模式属于行为型模式。

代码实现

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// 广播电台示例

class RadioStation { // 电台
    constructor(frequency) {
        this.frequency = frequency;
    }

    getFrequency() {
        return this.frequency;
    }
}

class StationList { // 迭代器
    constructor(){
        this.index = -1;
        this.stations = [];
    }

    get(i){
        return this.stations[this.index];
    }

    hasNext(){
        let index = this.index + 1;
        return this.stations[index] !== void 0;
    }

    next(){
        return this.stations[++this.index];
    }

    addStation(station) {
        this.stations.push(station);
    }

    removeStation(toRemove) {
        const toRemoveFrequency = toRemove.getFrequency();
        this.stations = this.stations.filter(station => station.getFrequency() !== toRemoveFrequency);
    }
}

(function(){
    const stationList = new StationList();
    stationList.addStation(new RadioStation(89));
    stationList.addStation(new RadioStation(101));
    stationList.addStation(new RadioStation(102));
    stationList.addStation(new RadioStation(103.2));
    stationList.stations.forEach(station => console.log(station.getFrequency())); // 89 101 102 103.2
    stationList.removeStation(new RadioStation(89));
    while(stationList.hasNext()) console.log(stationList.next().getFrequency()); // 101 102 103.2
})();

参考链接