迭代器模式

[louzhedong]

迭代器模式

它提供一种方法访问一个容器对象中各个元素，而又不需暴露该对象的内部细节

应用很广

到处都有它的身影

实现

Java

/**
 * 迭代器接口
 **/
public interface Iterator {
    Object next();
    boolean hasNext();
    boolean remove();
}

/**
 * 具体接口类
 **/
public class ConcreteIterator implements Iterator{
    private Vector vector = new Vector();
    public int cursor = 0;

    public ConcreteIterator(Vector _vector) {
        this.vector = _vector;
    }

    @Override
    public Object next() {
        Object result;
        if (this.hasNext()) {
            result = this.vector.get(this.cursor++);
        } else {
            result = null;
        }
        return result;
    }

    @Override
    public boolean hasNext() {
        if (this.cursor == this.vector.size()) {
            return false;
        } else {
            return true;
        }
    }

    @Override
    public boolean remove() {
        this.vector.remove(this.cursor);
        return true;
    }
}

/**
 * 抽象容器类
 **/
public interface Aggregate {
    void add(Object object);
    Iterator iterator();
}

/**
 * 具体容器类
 **/
public class ConcreteAggregate implements Aggregate{
    private Vector vector = new Vector();
    @Override
    public void add(Object object) {
        this.vector.add(object);
    }

    @Override
    public Iterator iterator() {
        return new ConcreteIterator(this.vector);
    }
}

/**
 * 场景类
 **/
public class Client {
    public static void main(String[] args) {
        Aggregate aggregate = new ConcreteAggregate();
        aggregate.add("a");
        aggregate.add("b");
        aggregate.add("c");

        Iterator iterator = aggregate.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

JavaScript

var each = function (array, callback) {
  for (var i = 0, l = array.length; i < l; i++) {
    callback.call(array[i], i, array[i]);
  }
}

each([1, 2, 3], function (i, n) {
  console.log([i, n]);
})