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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