Package form

 [](https://semaphoreci.com/joeybloggs/form) [](https://coveralls.io/github/go-playground/form?branch=master) [](https://goreportcard.com/report/github.com/go-playground/form) [](https://godoc.org/github.com/go-playground/form) 

Package form Decodes url.Values into struct values and Encodes struct values into url.Values.

It has the following features:

• Supports map of almost all types.
• Supports both Numbered and Normal arrays eg. "Array[0]" and just "Array" with multiple values passed.
• Array honours the specified index. eg. if "Array[2]" is the only Array value passed down, it will be put at index 2; if array isn't big enough it will be expanded.
• Only creates objects as necessary eg. if no array or map values are passed down, the array and map are left as their default values in the struct.
• Allows for Custom Type registration.
• Handles time.Time using RFC3339 time format by default, but can easily be changed by registering a Custom Type, see below.

Common Questions

• Does it support encoding.TextUnmarshaler? No because TextUnmarshaler only accepts []byte but posted values can have multiple values, so is not suitable.

Supported Types ( out of the box )

• string
• bool
• int, int8, int16, int32, int64
• uint, uint8, uint16, uint32, uint64
• float32, float64
• struct and anonymous struct
• interface{}
• time.Time - by default using RFC3339
• a pointer to one of the above types
• slice, array
• map
• custom types can override any of the above types
• many other types may be supported inherently (eg. bson.ObjectId is type ObjectId string, which will get populated by the string type

NOTE: map, struct and slice nesting are ad infinitum.

Installation

Use go get.

go get github.com/go-playground/form

Then import the form package into your own code.

import "github.com/go-playground/form"

Usage

• Use symbol . for separating fields/structs. (eg. structfield.field)
• Use [index or key] for access to index of a slice/array or key for map. (eg. arrayfield[0], mapfield[keyvalue])

<form method="POST">
  <input type="text" name="Name" value="joeybloggs"/>
  <input type="text" name="Age" value="3"/>
  <input type="text" name="Gender" value="Male"/>
  <input type="text" name="Address[0].Name" value="26 Here Blvd."/>
  <input type="text" name="Address[0].Phone" value="9(999)999-9999"/>
  <input type="text" name="Address[1].Name" value="26 There Blvd."/>
  <input type="text" name="Address[1].Phone" value="1(111)111-1111"/>
  <input type="text" name="active" value="true"/>
  <input type="text" name="MapExample[key]" value="value"/>
  <input type="text" name="NestedMap[key][key]" value="value"/>
  <input type="text" name="NestedArray[0][0]" value="value"/>
  <input type="submit"/>
</form>

Examples

Decoding

package main

import (
	"fmt"
	"log"
	"net/url"

	"github.com/go-playground/form"
)

// Address contains address information
type Address struct {
	Name  string
	Phone string
}

// User contains user information
type User struct {
	Name        string
	Age         uint8
	Gender      string
	Address     []Address
	Active      bool `form:"active"`
	MapExample  map[string]string
	NestedMap   map[string]map[string]string
	NestedArray [][]string
}

// use a single instance of Decoder, it caches struct info
var decoder *form.Decoder

func main() {
	decoder = form.NewDecoder()

	// this simulates the results of http.Request's ParseForm() function
	values := parseForm()

	var user User

	// must pass a pointer
	err := decoder.Decode(&user, values)
	if err != nil {
		log.Panic(err)
	}

	fmt.Printf("%#v\n", user)
}

// this simulates the results of http.Request's ParseForm() function
func parseForm() url.Values {
	return url.Values{
		"Name":                []string{"joeybloggs"},
		"Age":                 []string{"3"},
		"Gender":              []string{"Male"},
		"Address[0].Name":     []string{"26 Here Blvd."},
		"Address[0].Phone":    []string{"9(999)999-9999"},
		"Address[1].Name":     []string{"26 There Blvd."},
		"Address[1].Phone":    []string{"1(111)111-1111"},
		"active":              []string{"true"},
		"MapExample[key]":     []string{"value"},
		"NestedMap[key][key]": []string{"value"},
		"NestedArray[0][0]":   []string{"value"},
	}
}

Encoding

package main

import (
	"fmt"
	"log"

	"github.com/go-playground/form"
)

// Address contains address information
type Address struct {
	Name  string
	Phone string
}

// User contains user information
type User struct {
	Name        string
	Age         uint8
	Gender      string
	Address     []Address
	Active      bool `form:"active"`
	MapExample  map[string]string
	NestedMap   map[string]map[string]string
	NestedArray [][]string
}

// use a single instance of Encoder, it caches struct info
var encoder *form.Encoder

func main() {
	encoder = form.NewEncoder()

	user := User{
		Name:   "joeybloggs",
		Age:    3,
		Gender: "Male",
		Address: []Address{
			{Name: "26 Here Blvd.", Phone: "9(999)999-9999"},
			{Name: "26 There Blvd.", Phone: "1(111)111-1111"},
		},
		Active:      true,
		MapExample:  map[string]string{"key": "value"},
		NestedMap:   map[string]map[string]string{"key": {"key": "value"}},
		NestedArray: [][]string{{"value"}},
	}

	// must pass a pointer
	values, err := encoder.Encode(&user)
	if err != nil {
		log.Panic(err)
	}

	fmt.Printf("%#v\n", values)
}

Registering Custom Types

Decoder

decoder.RegisterCustomTypeFunc(func(vals []string) (interface{}, error) {
		return time.Parse("2006-01-02", vals[0])
	}, time.Time{})

Encoder

encoder.RegisterCustomTypeFunc(func(x interface{}) ([]string, error) {
		return []string{x.(time.Time).Format("2006-01-02")}, nil
	}, time.Time{})

Ignoring Fields

you can tell form to ignore fields using - in the tag

type MyStruct struct {
    Field string `form:"-"`
}

Notes

To maximize compatibility with other systems the Encoder attempts to avoid using array indexes in url.Values if at all possible.

eg.

// A struct field of
Field []string{"1", "2", "3"}

// will be output a url.Value as
"Field": []string{"1", "2", "3"}

and not
"Field[0]": []string{"1"}
"Field[1]": []string{"2"}
"Field[2]": []string{"3"}

// however there are times where it is unavoidable, like with pointers
i := int(1)
Field []*string{nil, nil, &i}

// to avoid index 1 and 2 must use index
"Field[2]": []string{"1"}

Benchmarks

Run on MacBook Pro (Retina, 15-inch, Late 2013) 2.6 GHz Intel Core i7 16 GB 1600 MHz DDR3 using Go version go1.6.2 darwin/amd64

NOTE: the 1 allocation and B/op in the first 4 decodes is actually the struct allocating when passing it in, so primitives are actually zero allocation.

go test -bench=. -benchmem=true

PASS
BenchmarkSimpleUserDecodeStruct-8                          	 5000000	       298 ns/op	      64 B/op	       1 allocs/op
BenchmarkSimpleUserDecodeStructParallel-8                  	20000000	        91.4 ns/op	      64 B/op	       1 allocs/op
BenchmarkSimpleUserEncodeStruct-8                          	 2000000	       966 ns/op	     549 B/op	      12 allocs/op
BenchmarkSimpleUserEncodeStructParallel-8                  	 5000000	       313 ns/op	     549 B/op	      12 allocs/op
BenchmarkPrimitivesDecodeStructAllPrimitivesTypes-8        	 1000000	      1010 ns/op	      96 B/op	       1 allocs/op
BenchmarkPrimitivesDecodeStructAllPrimitivesTypesParallel-8	 5000000	       285 ns/op	      96 B/op	       1 allocs/op
BenchmarkPrimitivesEncodeStructAllPrimitivesTypes-8        	  300000	      4718 ns/op	    3073 B/op	      47 allocs/op
BenchmarkPrimitivesEncodeStructAllPrimitivesTypesParallel-8	 1000000	      1673 ns/op	    3072 B/op	      47 allocs/op
BenchmarkComplexArrayDecodeStructAllTypes-8                	  100000	     16145 ns/op	    2289 B/op	     122 allocs/op
BenchmarkComplexArrayDecodeStructAllTypesParallel-8        	  300000	      4943 ns/op	    2291 B/op	     122 allocs/op
BenchmarkComplexArrayEncodeStructAllTypes-8                	  100000	     16020 ns/op	    7351 B/op	     147 allocs/op
BenchmarkComplexArrayEncodeStructAllTypesParallel-8        	  300000	      5129 ns/op	    7351 B/op	     147 allocs/op
BenchmarkComplexMapDecodeStructAllTypes-8                  	  100000	     22933 ns/op	    5338 B/op	     131 allocs/op
BenchmarkComplexMapDecodeStructAllTypesParallel-8          	  200000	      6366 ns/op	    5341 B/op	     131 allocs/op
BenchmarkComplexMapEncodeStructAllTypes-8                  	  100000	     16861 ns/op	    7161 B/op	     176 allocs/op
BenchmarkComplexMapEncodeStructAllTypesParallel-8          	  300000	      5159 ns/op	    7160 B/op	     176 allocs/op
BenchmarkDecodeNestedStruct-8                              	  500000	      3482 ns/op	     416 B/op	      15 allocs/op
BenchmarkDecodeNestedStructParallel-8                      	 2000000	      1011 ns/op	     416 B/op	      15 allocs/op
BenchmarkEncodeNestedStruct-8                              	 1000000	      2255 ns/op	     768 B/op	      17 allocs/op
BenchmarkEncodeNestedStructParallel-8                      	 2000000	       738 ns/op	     768 B/op	      17 allocs/op

Competitor benchmarks can be found here

Complimentary Software

Here is a list of software that compliments using this library post decoding.

• Validator - Go Struct and Field validation, including Cross Field, Cross Struct, Map, Slice and Array diving.
• Conform - Trims, sanitizes & scrubs data based on struct tags.

Package Versioning

I'm jumping on the vendoring bandwagon, you should vendor this package as I will not be creating different version with gopkg.in like allot of my other libraries.

Why? because my time is spread pretty thin maintaining all of the libraries I have + LIFE, it is so freeing not to worry about it and will help me keep pouring out bigger and better things for you the community.

License

Distributed under MIT License, please see license file in code for more details.