DesignPattern笔记(三)Iterator

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https://en.wikipedia.org/wiki/Iterator_pattern


参考C#中的IEnumerable和IEnumerator接口, 以string为例(代码摘自C# 5.0 in a nutshell第4章和第7章相关章节)

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string s = "Hello";
// Because string implements IEnumerable, we can call GetEnumerator():
IEnumerator rator = s.GetEnumerator();
while (rator.MoveNext())
{
	char c = (char) rator.Current;
	Console.Write (c + ".");
}
// Output: H.e.l.l.o.

IEnumerable接口等同于Aggregate接口
IEnumerator接口等同于Iterator接口

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public interface IEnumerable
{
	IEnumerator GetEnumerator();
}

public interface IEnumerator
{
	bool MoveNext();
	object Current { get; }
	void Reset();
}

GetEnumerator方法等同于CreateInterator方法
string实现IEnumerable接口. CharEnumerator实现IEnumerator, IEnumerator接口(http://referencesource.microsoft.com/#mscorlib/system/charenumerator.cs,a6b81e2669b87db5)

这是C# 1.0. 之后用法上引入了foreach, 实现上引入了yield return.