实现自定义集合

我们可以通过实现 IEnumberable 接口和 IEnumerator 接口实现自定义集合。

public class MySet : IEnumerable
{
    internal object[] values;
    public MySet(object[] values)
    {
        this.values = values;
    }
    public IEnumerator GetEnumerator()
    {
        return new MySetIterator(this);
    }
}
//实现自定义迭代器：
public class MySetIterator : IEnumerator
{
    MySet set;
    int position;
    internal MySetIterator(MySet set)
    {
        this.set = set;
        position = -1;
    }    
    public object Current
    {
        get
        {
            if (position == -1 || position == set.values.Length)
            {
                throw new InvalidOperationException();
            }
            int index = position;
            return set.values[index];
        }
    }
    public bool MoveNext()
    {
        if (position != set.values.Length)
        {
            position++;
        }
        return position < set.values.Length;
    }
    public void Reset()
    {
        position = -1;
    }
}

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*** No matter how far you go, looking back is also necessary. ***

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