Golang集合遍历方法与迭代器模式应用

type IntSliceIterator struct {
  data []int
  index int
}

func NewIntSliceIterator(data []int) *IntSliceIterator {
  return &IntSliceIterator{data: data, index: 0}
}

func (it *IntSliceIterator) HasNext() bool {
  return it.index < len(it.data)
}

func (it *IntSliceIterator) Next() int {
  if !it.HasNext() {
    panic("no more elements")
  }
  value := it.data[it.index]
  it.index++
  return value
}

data := []int{1, 2, 3, 4, 5}
it := NewIntSliceIterator(data)
for it.HasNext() {
  fmt.Println(it.Next())
}

type SliceIterator[T any] struct {
  data []T
  index int
}

func NewSliceIterator[T any](data []T) *SliceIterator[T] {
  return &SliceIterator[T]{data: data, index: 0}
}

func (it *SliceIterator[T]) HasNext() bool {
  return it.index < len(it.data)
}

func (it *SliceIterator[T]) Next() T {
  if !it.HasNext() {
    var zero T
    return zero
  }
  value := it.data[it.index]
  it.index++
  return value
}

it := NewSliceIterator([]string{"a", "b", "c"})
for it.HasNext() {
  fmt.Println(it.Next())
}

type StringSet struct {
  items map[string]struct{}
}

func (s *StringSet) Add(str string) {
  s.items[str] = struct{}{}
}

func (s *StringSet) Iterator() *StringSetIterator {
  keys := make([]string, 0, len(s.items))
  for k := range s.items {
    keys = append(keys, k)
  }
  return &StringSetIterator{data: keys, index: 0}
}

type StringSetIterator struct {
  data []string
  index int
}

func (it *StringSetIterator) HasNext() bool { return it.index < len(it.data) }
func (it *StringSetIterator) Next() string {
  if !it.HasNext() { return "" }
  v := it.data[it.index]
  it.index++
  return v
}

set := &StringSet{items: make(map[string]struct{})}
set.Add("x"); set.Add("y")
it := set.Iterator()
for it.HasNext() {
  fmt.Println(it.Next())
}