关于golang:聊聊gost的Pager

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本文次要钻研一下 gost 的 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 办法

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 办法返回的是 len(d.GetData())；其 HasData 办法应用 d.GetDataSize() > 0 来判断

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 办法依据 requestOffset、pageSize、data、totalSize 来结构 Page；它会计算 totalPages、hasNext

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())
}

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