Golang如何实现迭代器模式与懒加载结合_Golang 迭代器模式优化实践

type Iterator interface {
    Next() bool
    Value() interface{}
}

type User struct {
    ID   int
    Name string
}

type UserIterator struct {
    rows    *sql.Rows // 假设使用database/sql包
    hasNext bool
    err     error
}

func (it *UserIterator) Next() bool {
    if it.err != nil {
        return false
    }
    it.hasNext = it.rows.Next()
    return it.hasNext
}

func (it *UserIterator) Value() interface{} {
    if !it.hasNext {
        return nil
    }
    var user User
    err := it.rows.Scan(&user.ID, &user.Name)
    if err != nil {
        it.err = err
        return nil
    }
    return user
}

type Iterator[T any] interface {
    Next() bool
    Value() T
}

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

func NewSliceIterator[T any](data []T) *SliceIterator[T] {
    return &SliceIterator[T]{slice: data, index: -1}
}

func (it *SliceIterator[T]) Next() bool {
    it.index++
    return it.index < len(it.slice)
}

func (it *SliceIterator[T]) Value() T {
    if it.index < 0 || it.index >= len(it.slice) {
        var zero T
        return zero
    }
    return it.slice[it.index]
}

nums := []int{1, 2, 3}
it := NewSliceIterator(nums)
for it.Next() {
    fmt.Println(it.Value()) // 直接返回int
}