go - 在这两个迭代器中减少重复的好方法是什么？

Question

我编写了一个迭代器以便更轻松地访问某些分页数据库结果，但减少重复的好方法是什么？

foo_iterator.go

type FooIterator struct {
    hasNext   bool
    app       *App
    batchSize int
}

func NewFooIterator(app *App, batchSize int) *FooIterator {
    return &FooIterator{
        hasNext:   true,
        app:       app,
        batchSize: batchSize,
    }
}

func (it *FooIterator) HasNext() bool {
    return it.hasNext
}

func (it *FooIterator) Next() []*model.Foo {
    offset := 0
    batch := it.app.GetAllFoosInPages(offset, it.batchSize)
    if len(batch) < it.batchSize {
        it.hasNext = false
    }
    offset += it.batchSize
    return batch
}

bar_iterator.go

type BarIterator struct {
    hasNext   bool
    app       *App
    batchSize int
}

func NewBarIterator(app *App, batchSize int) *BarIterator {
    return &BarIterator{
        hasNext:   true,
        app:       app,
        batchSize: batchSize,
    }
}

func (it *BarIterator) HasNext() bool {
    return it.hasNext
}

func (it *BarIterator) Next() []*model.Bar {
    offset := 0
    batch := it.app.GetAllBarsInPages(offset, it.batchSize)
    if len(batch) < bi.batchSize {
        it.hasNext = false
    }
    offset += it.batchSize
    return batch
}

用法

fooIterator := NewFooIterator(a, 100)

for fooIterator.HasNext() {
    fooBatch := rolesIterator.Next()
    // Do stuff
}

它们非常相似，肯定有一些共享代码的好方法，但我尝试的一切似乎都很尴尬。

Answer 1

编写一个通用迭代器调用一个函数来获取更多数据:

type Iterator struct {
    more      func(offset int, batchSize int) (int, interface{})
    hasNext   bool
    batchSize int
    offset    int
}

func (it *Iterator) HasNext() bool {
    return it.hasNext
}

func (it *Iterator) Next() interface{} {
    n, batch := it.more(it.offset, it.batchSize)
    if n < it.batchSize {
        it.hasNext = false
    }
    it.offset += n
    return batch
}

像这样使用它:

func NewFooIterator(app *App, batchSize int) *Iterator {
    return &Iterator{
        hasNext:   true,
        batchSize: batchSize,
        more: func(offset int, batchSize int) (int, interface{}) {
            batch := it.app.GetAllFoosInPages(offset, it.batchSize)
            return len(batch), batch
        },
    }
}

fooIterator := NewFooIterator(a, 100)

for fooIterator.HasNext() {
    fooBatch := fooIterator.Next().([]*model.Foo)
    // Do stuff
}