form

README

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 Go value(s) and Encodes Go value(s) 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.
• Handles Encoding & Decoding of almost all Go types eg. can Decode into struct, array, map, int... and Encode a struct, array, map, int...

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 go1.6.3 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	       318 ns/op	      64 B/op	       1 allocs/op
BenchmarkSimpleUserDecodeStructParallel-8                  	20000000	        95.2 ns/op	      64 B/op	       1 allocs/op
BenchmarkSimpleUserEncodeStruct-8                          	 1000000	      1000 ns/op	     549 B/op	      12 allocs/op
BenchmarkSimpleUserEncodeStructParallel-8                  	 5000000	       325 ns/op	     549 B/op	      12 allocs/op
BenchmarkPrimitivesDecodeStructAllPrimitivesTypes-8        	 1000000	      1058 ns/op	      96 B/op	       1 allocs/op
BenchmarkPrimitivesDecodeStructAllPrimitivesTypesParallel-8	 5000000	       324 ns/op	      96 B/op	       1 allocs/op
BenchmarkPrimitivesEncodeStructAllPrimitivesTypes-8        	  300000	      4823 ns/op	    3073 B/op	      47 allocs/op
BenchmarkPrimitivesEncodeStructAllPrimitivesTypesParallel-8	 1000000	      1732 ns/op	    3072 B/op	      47 allocs/op
BenchmarkComplexArrayDecodeStructAllTypes-8                	  100000	     16340 ns/op	    2289 B/op	     122 allocs/op
BenchmarkComplexArrayDecodeStructAllTypesParallel-8        	  300000	      5105 ns/op	    2291 B/op	     122 allocs/op
BenchmarkComplexArrayEncodeStructAllTypes-8                	  100000	     16343 ns/op	    7351 B/op	     147 allocs/op
BenchmarkComplexArrayEncodeStructAllTypesParallel-8        	  300000	      5969 ns/op	    7351 B/op	     147 allocs/op
BenchmarkComplexMapDecodeStructAllTypes-8                  	  100000	     21259 ns/op	    5338 B/op	     131 allocs/op
BenchmarkComplexMapDecodeStructAllTypesParallel-8          	  200000	      7493 ns/op	    5342 B/op	     131 allocs/op
BenchmarkComplexMapEncodeStructAllTypes-8                  	  100000	     17060 ns/op	    7161 B/op	     176 allocs/op
BenchmarkComplexMapEncodeStructAllTypesParallel-8          	  300000	      6421 ns/op	    7161 B/op	     176 allocs/op
BenchmarkDecodeNestedStruct-8                              	  300000	      3488 ns/op	     416 B/op	      15 allocs/op
BenchmarkDecodeNestedStructParallel-8                      	 1000000	      1203 ns/op	     416 B/op	      15 allocs/op
BenchmarkEncodeNestedStruct-8                              	 1000000	      2286 ns/op	     768 B/op	      17 allocs/op
BenchmarkEncodeNestedStructParallel-8                      	 2000000	       939 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.

Documentation

Overview

Package form Decodes url.Values into Go value(s) and Encodes Go value(s) into url.Values.

It has the following features:

• Primitives types cause zero allocations.
• 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.
• Handles Encoding & Decoding of almost all Go types eg. can Decode into struct, array, map, int... and Encode a struct, array, map, int...

Common Questions

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 supported types

• 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.

Usage

symbols

• 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]`)

html

<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>

Example

example decoding the above HTML

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"},
    }
}

example 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"}

Index

• func ExtractType(current reflect.Value) (reflect.Value, reflect.Kind)
• type DecodeCustomTypeFunc
• type DecodeErrors
  • func (d DecodeErrors) Error() string
• type Decoder
  • func NewDecoder() *Decoder
  • func (d *Decoder) Decode(v interface{}, values url.Values) (err error)
  • func (d *Decoder) RegisterCustomTypeFunc(fn DecodeCustomTypeFunc, types ...interface{})
  • func (d *Decoder) SetMaxArraySize(size uint)
  • func (d *Decoder) SetTagName(tagName string)
• type EncodeCustomTypeFunc
• type EncodeErrors
  • func (e EncodeErrors) Error() string
• type Encoder
  • func NewEncoder() *Encoder
  • func (e *Encoder) Encode(v interface{}) (url.Values, error)
  • func (e *Encoder) RegisterCustomTypeFunc(fn EncodeCustomTypeFunc, types ...interface{})
  • func (e *Encoder) SetTagName(tagName string)
• type InvalidDecoderError
  • func (e *InvalidDecoderError) Error() string
• type InvalidEncodeError
  • func (e *InvalidEncodeError) Error() string

Functions

func ExtractType

func ExtractType(current reflect.Value) (reflect.Value, reflect.Kind)

ExtractType gets the actual underlying type of field value. it is exposed for use within you Custom Functions

Types

type DecodeCustomTypeFunc

type DecodeCustomTypeFunc func([]string) (interface{}, error)

DecodeCustomTypeFunc allows for registering/overriding types to be parsed.

type DecodeErrors

type DecodeErrors map[string]error

DecodeErrors is a map of errors encountered during form decoding

func (DecodeErrors) Error

func (d DecodeErrors) Error() string

type Decoder

type Decoder struct {
	// contains filtered or unexported fields
}

Decoder is the main decode instance

func NewDecoder

func NewDecoder() *Decoder

NewDecoder creates a new decoder instance with sane defaults

func (*Decoder) Decode

func (d *Decoder) Decode(v interface{}, values url.Values) (err error)

Decode parses the given values and sets the corresponding struct and/or type values

Decode returns an InvalidDecoderError if interface passed is invalid.

func (*Decoder) RegisterCustomTypeFunc

func (d *Decoder) RegisterCustomTypeFunc(fn DecodeCustomTypeFunc, types ...interface{})

RegisterCustomTypeFunc registers a CustomTypeFunc against a number of types NOTE: this method is not thread-safe it is intended that these all be registered prior to any parsing

func (*Decoder) SetMaxArraySize

func (d *Decoder) SetMaxArraySize(size uint)

SetMaxArraySize sets maximum array size that can be created. This limit is for the array indexing this library supports to avoid potential DOS or man-in-the-middle attacks using an unusually high number. DEFAULT: 10000

func (*Decoder) SetTagName

func (d *Decoder) SetTagName(tagName string)

SetTagName sets the given tag name to be used by the decoder. Default is "form"

type EncodeCustomTypeFunc

type EncodeCustomTypeFunc func(x interface{}) ([]string, error)

EncodeCustomTypeFunc allows for registering/overriding types to be parsed.

type EncodeErrors

type EncodeErrors map[string]error

EncodeErrors is a map of errors encountered during form encoding

func (EncodeErrors) Error

func (e EncodeErrors) Error() string

type Encoder

type Encoder struct {
	// contains filtered or unexported fields
}

Encoder is the main encode instance

func NewEncoder

func NewEncoder() *Encoder

NewEncoder creates a new encoder instance with sane defaults

func (*Encoder) Encode

func (e *Encoder) Encode(v interface{}) (url.Values, error)

Encode encodes the given values and sets the corresponding struct values

func (*Encoder) RegisterCustomTypeFunc

func (e *Encoder) RegisterCustomTypeFunc(fn EncodeCustomTypeFunc, types ...interface{})

RegisterCustomTypeFunc registers a CustomTypeFunc against a number of types NOTE: this method is not thread-safe it is intended that these all be registered prior to any parsing

func (*Encoder) SetTagName

func (e *Encoder) SetTagName(tagName string)

SetTagName sets the given tag name to be used by the decoder. Default is "form"

type InvalidDecoderError

type InvalidDecoderError struct {
	Type reflect.Type
}

An InvalidDecoderError describes an invalid argument passed to Decode. (The argument passed to Decode must be a non-nil pointer.)

func (*InvalidDecoderError) Error

func (e *InvalidDecoderError) Error() string

type InvalidEncodeError

type InvalidEncodeError struct {
	Type reflect.Type
}

An InvalidEncodeError describes an invalid argument passed to Encode.

func (*InvalidEncodeError) Error

func (e *InvalidEncodeError) Error() string