pagination-go

This is a helper library which perfectly matches for server-side implementation of @gemcook/pagination

Installation

go get -u github.com/gemcook/pagination-go

If you use dep

dep ensure -add github.com/gemcook/pagination-go

Usage

fetcher interface

Your fetching object must implement fetcher interface.

type PageFetcher interface {
	Count(cond interface{}) (int, error)
	FetchPage(cond interface{}, input *PageFetchInput, result *PageFetchResult) error
}

type PageFetchInput struct {
	Limit  int
	Offset int
	Orders []*Order
}

parse Function

Package pagination provides ParseQuery and ParseMap functions that parses Query Parameters from request URL. Those query parameters below will be parsed.

query parameter	Mapped field	required	expected value	default value
limit	Limit	no	positive integer	10
page	Page	no	positive integer (1~)	1
pagination	Enabled	no	boolean	true

Query String from URL

// RequestURI: https://example.com/fruits?limit=10&page=1&price_range=100,300&sort=+price&pagination=true
p := pagination.ParseQuery(r.URL.RequestURI())

fmt.Println("limit =", p.Limit)
fmt.Println("page =", p.Page)
fmt.Println("pagination =", p.Enabled)

Query Parameters from AWS API Gateway - Lambda

import "github.com/aws/aws-lambda-go/events"

func Handler(event events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
	// event.QueryStringParameters
	// map[string]string{"limit": "10", "page": "1", "pagination": "false"}

	p := pagination.ParseMap(event.QueryStringParameters)
	fmt.Println("limit =", p.Limit)
	fmt.Println("page =", p.Page)
	fmt.Println("pagination =", p.Enabled)
}

fetching condition [OPTIONAL]

Tell pagination the condition to filter resources. Then use cond interface{} in Count and FetchPage function. Use type assertion for cond to restore your fetching condition object.

Orders [OPTIONAL]

Optionally, pagination takes orders. Use pagination.ParseQuery or pagination.ParseMap to parse sort parameter in query string. Then, just pass Query.Sort to Setting.Orders.

Those query parameters below will be parsed.

query parameter	Mapped field	required	expected value	default value
sort	Sort	no	+column_name for ascending sort. -column_name for descending sort.	nil

Example

import (
    "http/net"
    "encoding/json"
    "strconv"

    "github.com/gemcook/pagination-go"
)

type fruitFetcher struct{}

type FruitCondition struct{
    PriceLowerLimit int
    PriceHigherLimit int
}

func ParseFruitCondition(uri string) *FruitCondition {
    // parse uri and initialize struct
}

func handler(w http.ResponseWriter, r *http.Request) {
	// RequestURI: https://example.com/fruits?limit=10&page=1&price_range=100,300&sort=+price
	p := pagination.ParseQuery(r.URL.RequestURI())
	cond := parseFruitCondition(r.URL.RequestURI())
	fetcher := newFruitFetcher()

	totalCount, totalPages, res, err := pagination.Fetch(fetcher, &pagination.Setting{
		Limit:      p.Limit,
		Page:       p.Page,
		Cond:       cond,
		Orders:     p.Sort,
	})

	if err != nil {
		w.Header().Set("Content-Type", "text/html; charset=utf8")
		w.WriteHeader(400)
		fmt.Fprintf(w, "something wrong: %v", err)
		return
	}

	w.Header().Set("X-Total-Count", strconv.Itoa(totalCount))
	w.Header().Set("X-Total-Pages", strconv.Itoa(totalPages))
	w.Header().Set("Access-Control-Expose-Headers", "X-Total-Count,X-Total-Pages")
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(200)
	resJSON, _ := json.Marshal(res)
	w.Write(resJSON)
}

For full source code, see example/server.go.

Run example.

cd example
go run server.go

Then open http://localhost:8080/fruits?limit=2&page=1&price_range=100,300&sort=+price