《大话设计模式-Golang》迭代器模式

概念

迭代器模式（IteratorPattern）：提供一种方法顺序访问一个聚集对象中各个元素，而又不暴露该对象的内部表示。

需求

利用迭代器模式实现售票员售票

UML图

代码

抽象聚集类

type Aggregate interface {
	CreateIterator() Iterator
}

抽象迭代器类

type Iterator interface {
	First() interface{}
	Next() interface{}
	IsDone() bool
	CurrentItem() interface{}
}

具体聚集类

type ConcreteAggregate struct {
	Items []interface{}
}

func (c *ConcreteAggregate) CreateIterator() Iterator {
	return &ConcreteIterator{Aggregate: *c}
}

具体迭代器类

type ConcreteIterator struct {
	Aggregate ConcreteAggregate
	current   int64
}

func (c *ConcreteIterator) First() interface{} {
	return c.Aggregate.Items[0]
}

func (c *ConcreteIterator) Next() interface{} {
	var ret interface{}
	c.current++
	if c.current < int64(len(c.Aggregate.Items)) {
		ret = c.Aggregate.Items[c.current]
	}
	return ret
}

func (c *ConcreteIterator) IsDone() bool {
	return c.current < int64(len(c.Aggregate.Items))
}

func (c *ConcreteIterator) CurrentItem() interface{} {
	return c.Aggregate.Items[c.current]
}

测试

//迭代器模式
a := iteratorPattern.ConcreteAggregate{}
a.Items = append(a.Items, "大鸟")
a.Items = append(a.Items, "小菜")
a.Items = append(a.Items, "行李")
a.Items = append(a.Items, "老外")
a.Items = append(a.Items, "公交内部员工")
a.Items = append(a.Items, "小偷")

i := iteratorPattern.ConcreteIterator{Aggregate: a}
for i.IsDone() {
	fmt.Printf("%v 请买车票", i.CurrentItem())
	fmt.Println()
	i.Next()
}