Golang如何应用迭代器模式遍历集合

type Iterator interface {
    HasNext() bool
    Next() interface{}
}
<p>type SliceIterator struct {
slice []interface{}
index int
}</p><p>func (it *SliceIterator) HasNext() bool {
return it.index < len(it.slice)
}</p><p>func (it *SliceIterator) Next() bool {
if it.HasNext() {
val := it.slice[it.index]
it.index++
return val
}
return nil
}</p>

data := []interface{}{"a", "b", "c"}
iter := &SliceIterator{slice: data, index: 0}
for iter.HasNext() {
    fmt.Println(iter.Next())
}

func IntGenerator(start, end int) <-chan int {
    ch := make(chan int)
    go func() {
        for i := start; i < end; i++ {
            ch <- i
        }
        close(ch)
    }()
    return ch
}

for num := range IntGenerator(1, 5) {
    fmt.Println(num)
}

type TreeNode struct {
    Val   int
    Left  *TreeNode
    Right *TreeNode
}
<p>type InOrderIterator struct {
stack []<em>TreeNode
curr  </em>TreeNode
}</p><p>func NewInOrderIterator(root <em>TreeNode) </em>InOrderIterator {
return &InOrderIterator{curr: root}
}</p><p>func (it *InOrderIterator) HasNext() bool {
return it.curr != nil || len(it.stack) > 0
}</p><p>func (it *InOrderIterator) Next() int {
for it.curr != nil {
it.stack = append(it.stack, it.curr)
it.curr = it.curr.Left
}</p><pre class='brush:php;toolbar:false;'>node := it.stack[len(it.stack)-1]
it.stack = it.stack[:len(it.stack)-1]
val := node.Val
it.curr = node.Right
return val

func MakeCounter(start, step int) func() int {
    current := start
    return func() int {
        defer func() { current += step }()
        return current
    }
}

next := MakeCounter(1, 2)
for i := 0; i < 5; i++ {
    fmt.Println(next()) // 输出 1, 3, 5, 7, 9
}