This package provides an easy way to marshal and unmarshal url query string data to and from structs.

This was originally forked from dyninc/qstring but it seems to have become inactive and I wanted some extra features so I am now maintaining this fork.

$ go get github.com/Southclaws/qstring

package main

import (
	"net/http"

	"github.com/Southclaws/qstring"
)

// Query is the http request query struct.
type Query struct {
	Names    []string
	Limit     int
	Page      int
}

func handler(w http.ResponseWriter, req *http.Request) {
	query := &Query{}
	err := qstring.Unmarshal(req.Url.Query(), query)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
	}

	// ... run conditional logic based on provided query parameters
}

The above example will unmarshal the query string from an http.Request and unmarshal it into the provided struct. This means that a query of ?names=foo&names=bar&limit=50&page=1 would be unmarshaled into a struct similar to the following:

Query{
	Names: []string{"foo", "bar"},
	Limit: 50,
	Page: 1,
}

qstring also exposes two methods of Marshaling structs into Query parameters, one will Marshal the provided struct into a raw query string, the other will Marshal a struct into a url.Values type. Some Examples of both follow.

package main

import (
	"fmt"
	"net/http"

	"github.com/Southclaws/qstring"
)

// Query is the http request query struct.
type Query struct {
	Names    []string
	Limit     int
	Page      int
}

func main() {
	query := &Query{
		Names: []string{"foo", "bar"},
		Limit: 50,
		Page: 1,
	}
	q, err := qstring.MarshalString(query)
	fmt.Println(q)
	// Output: names=foo&names=bar&limit=50&page=1
}

package main

import (
	"fmt"
	"net/http"

	"github.com/Southclaws/qstring"
)

// Query is the http request query struct.
type Query struct {
	Names    []string
	Limit     int
	Page      int
}

func main() {
	query := &Query{
		Names: []string{"foo", "bar"},
		Limit: 50,
		Page: 1,
	}
	q, err := qstring.Marshal(query)
	fmt.Println(q)
	// Output: map[names:[foo, bar] limit:[50] page:[1]]
}

In the same spirit as other Unmarshaling libraries, qstring allows you to Marshal/Unmarshal nested structs

package main

import (
	"net/http"

	"github.com/Southclaws/qstring"
)

// PagingParams represents common pagination information for query strings
type PagingParams struct {
	Page int
	Limit int
}

// Query is the http request query struct.
type Query struct {
	Names    []string
	PageInfo PagingParams
}

Again, in the spirit of other Unmarshaling libraries, qstring allows for some more complex types, such as pointers and time.Time fields. A more complete example might look something like the following code snippet

package main

import (
	"time"
)

// PagingParams represents common pagination information for query strings
type PagingParams struct {
	Page int	`qstring:"page"`
	Limit int `qstring:"limit"`
}

// Query is the http request query struct.
type Query struct {
	Names    []string
	IDs      []int
	PageInfo *PagingParams
	Created  time.Time
	Modified time.Time
}

• All Timestamps are assumed to be in RFC3339 format
• A struct field tag of qstring is supported and supports all of the features you've come to know and love from Go (un)marshalers.
  • A field tag with a value of qstring:"-" instructs qstring to ignore the field.
  • A field tag with an the omitempty option set will be ignored if the field being marshaled has a zero value. qstring:"name,omitempty"
  • A slice field tag with the comma option set will produce a comma-separated list of items in a single query parameter instead of multiple instances of the parameter. qstring:"names,comma" will produce ?names=a,b,c instead of ?names=a&names=b&names=c.

In order to facilitate more complex queries qstring also provides some custom fields to save you a bit of headache with custom marshal/unmarshaling logic. Currently the following custom fields are provided:

• qstring.ComparativeTime - Supports timestamp query parameters with optional logical operators (<, >, <=, >=) such as ?created<=2006-01-02T15:04:05Z

BenchmarkUnmarshall-4 	  500000	      2711 ns/op	     448 B/op	      23 allocs/op
BenchmarkRawPLiteral-4	 1000000	      1675 ns/op	     448 B/op	      23 allocs/op
ok  	github.com/Southclaws/qstring	3.163s