[设计模式 Go实现] 行为型～迭代器模式

package iterator

import "fmt"

type Aggregate interface {
    Iterator() Iterator
}

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

type Numbers struct {
    start, end int
}

func NewNumbers(start, end int) *Numbers {
    return &Numbers{
        start: start,
        end:   end,
    }
}

func (n *Numbers) Iterator() Iterator {
    return &NumbersIterator{
        numbers: n,
        next:    n.start,
    }
}

type NumbersIterator struct {
    numbers *Numbers
    next    int
}

func (i *NumbersIterator) First() {
    i.next = i.numbers.start
}

func (i *NumbersIterator) IsDone() bool {
    return i.next > i.numbers.end
}

func (i *NumbersIterator) Next() interface{} {
    if !i.IsDone() {
        next := i.next
        i.next++
        return next
    }
    return nil
}

func IteratorPrint(i Iterator) {
    for i.First(); !i.IsDone(); {
        c := i.Next()
        fmt.Printf("%#v\n", c)
    }
}

package iterator

func ExampleIterator() {
    var aggregate Aggregate
    aggregate = NewNumbers(1, 10)

    IteratorPrint(aggregate.Iterator())
    // Output:
    // 1
    // 2
    // 3
    // 4
    // 5
    // 6
    // 7
    // 8
    // 9
    // 10
}