聊聊gost的Pager

序

本文主要研究一下gost的Pager

Pager

gost/hash/page/pager.go

// Pager is the abstraction for pagination usage.
type Pager interface {

    // GetOffset will return the offset
    GetOffset() int

    // GetPageSize will return the page size
    GetPageSize() int

    // GetTotalPages will return the number of total pages
    GetTotalPages() int

    // GetData will return the data
    GetData() []interface{}

    // GetDataSize will return the size of data.
    // Usually it's len(GetData())
    GetDataSize() int

    // HasNext will return whether has next page
    HasNext() bool

    // HasData will return whether this page has data.
    HasData() bool
}

Pager接口定义了GetOffset、GetPageSize、GetTotalPages、GetData、GetDataSize、HasNext、HasData方法

Page

gost/hash/page/page.go

// Page is the default implementation of Pager interface
type Page struct {
    requestOffset int
    pageSize      int
    totalSize     int
    data          []interface{}
    totalPages    int
    hasNext       bool
}

// GetOffSet will return the offset
func (d *Page) GetOffset() int {
    return d.requestOffset
}

// GetPageSize will return the page size
func (d *Page) GetPageSize() int {
    return d.pageSize
}

// GetTotalPages will return the number of total pages
func (d *Page) GetTotalPages() int {
    return d.totalPages
}

// GetData will return the data
func (d *Page) GetData() []interface{} {
    return d.data
}

// GetDataSize will return the size of data.
// it's len(GetData())
func (d *Page) GetDataSize() int {
    return len(d.GetData())
}

// HasNext will return whether has next page
func (d *Page) HasNext() bool {
    return d.hasNext
}

// HasData will return whether this page has data.
func (d *Page) HasData() bool {
    return d.GetDataSize() > 0
}

Page定义了requestOffset、pageSize、totalSize、data、totalPages、hasNext属性；它实现了Pager接口，其GetDataSize方法返回的是len(d.GetData())；其HasData方法使用 d.GetDataSize() > 0来判断

NewPage

gost/hash/page/page.go

// NewPage will create an instance
func NewPage(requestOffset int, pageSize int,
    data []interface{}, totalSize int) *Page {

    remain := totalSize % pageSize
    totalPages := totalSize / pageSize
    if remain > 0 {
        totalPages++
    }

    hasNext := totalSize-requestOffset-pageSize > 0

    return &Page{
        requestOffset: requestOffset,
        pageSize:      pageSize,
        data:          data,
        totalSize:     totalSize,
        totalPages:    totalPages,
        hasNext:       hasNext,
    }
}

NewPage方法根据requestOffset、pageSize、data、totalSize来构造Page；它会计算totalPages、hasNext

实例

gost/hash/page/page_test.go

func TestNewDefaultPage(t *testing.T) {
    data := make([]interface{}, 10)
    page := NewPage(121, 10, data, 499)

    assert.Equal(t, 10, page.GetDataSize())
    assert.Equal(t, 121, page.GetOffset())
    assert.Equal(t, 10, page.GetPageSize())
    assert.Equal(t, 50, page.GetTotalPages())
    assert.Equal(t, data, page.GetData())
    assert.True(t, page.HasNext())
    assert.True(t, page.HasData())

    page = NewPage(492, 10, data, 499)
    assert.False(t, page.HasNext())
}

小结

gost的Pager接口定义了GetOffset、GetPageSize、GetTotalPages、GetData、GetDataSize、HasNext、HasData方法；Page定义了requestOffset、pageSize、totalSize、data、totalPages、hasNext属性；它实现了Pager接口。

doc

• gost