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. - Slice honours the specified index. eg. if "Slice[2]" is the only Slice value passed down, it will be put at index 2; if slice isn't big enough it will be expanded.
- 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 a warning will be printed and value ignored.
- Only creates objects as necessary eg. if no
arrayormapvalues are passed down, thearrayandmapare 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.
- Mixing
array/slicewitharray[idx]/slice[idx], in which order are they parsed?array/slicethenarray[idx]/slice[idx]
stringboolint,int8,int16,int32,int64uint,uint8,uint16,uint32,uint64float32,float64structandanonymous structinterface{}time.Time- by default using RFC3339- a
pointerto one of the above types slice,arraymapcustom typescan override any of the above types- many other types may be supported inherently
NOTE: map, struct and slice nesting are ad infinitum.
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/v4"
- 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>Decoding
package main
import (
"fmt"
"log"
"net/url"
"github.com/go-playground/form/v4"
)
// 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/v4"
)
// 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)
}Decoder
decoder.RegisterCustomTypeFunc(func(vals []string) (interface{}, error) {
return time.Parse("2006-01-02", vals[0])
}, time.Time{})ADDITIONAL: if a struct type is registered, the function will only be called if a url.Value exists for the struct and not just the struct fields eg. url.Values{"User":"Name%3Djoeybloggs"} will call the custom type function with 'User' as the type, however url.Values{"User.Name":"joeybloggs"} will not.
Encoder
encoder.RegisterCustomTypeFunc(func(x interface{}) ([]string, error) {
return []string{x.(time.Time).Format("2006-01-02")}, nil
}, time.Time{})you can tell form to ignore fields using - in the tag
type MyStruct struct {
Field string `form:"-"`
}you can tell form to omit empty fields using ,omitempty or FieldName,omitempty in the tag
type MyStruct struct {
Field string `form:",omitempty"`
Field2 string `form:"CustomFieldName,omitempty"`
}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"}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 -run=NONE -bench=. -benchmem ./...
goos: darwin
goarch: arm64
pkg: github.com/go-playground/form/v4
cpu: Apple M3 Max
BenchmarkNestedArrayDecode100-16 75 15782643 ns/op 18754349 B/op 360810 allocs/op
BenchmarkNestedArrayDecode1000-16 1 2227892458 ns/op 1877558216 B/op 36011385 allocs/op
PASS
ok github.com/go-playground/form/v4 4.251s
goos: darwin
goarch: arm64
pkg: github.com/go-playground/form/v4/benchmarks
cpu: Apple M3 Max
BenchmarkSimpleUserDecodeStruct-16 12669696 94.60 ns/op 64 B/op 1 allocs/op
BenchmarkSimpleUserDecodeStructParallel-16 46715631 27.79 ns/op 64 B/op 1 allocs/op
BenchmarkSimpleUserEncodeStruct-16 4624094 256.7 ns/op 485 B/op 10 allocs/op
BenchmarkSimpleUserEncodeStructParallel-16 7386290 166.2 ns/op 485 B/op 10 allocs/op
BenchmarkPrimitivesDecodeStructAllPrimitivesTypes-16 3533421 332.3 ns/op 96 B/op 1 allocs/op
BenchmarkPrimitivesDecodeStructAllPrimitivesTypesParallel-16 20706642 59.43 ns/op 96 B/op 1 allocs/op
BenchmarkPrimitivesEncodeStructAllPrimitivesTypes-16 1228750 966.4 ns/op 1465 B/op 34 allocs/op
BenchmarkPrimitivesEncodeStructAllPrimitivesTypesParallel-16 1962678 607.2 ns/op 1465 B/op 34 allocs/op
BenchmarkComplexArrayDecodeStructAllTypes-16 213568 5361 ns/op 2081 B/op 121 allocs/op
BenchmarkComplexArrayDecodeStructAllTypesParallel-16 960226 1314 ns/op 2087 B/op 121 allocs/op
BenchmarkComplexArrayEncodeStructAllTypes-16 271944 4017 ns/op 6788 B/op 107 allocs/op
BenchmarkComplexArrayEncodeStructAllTypesParallel-16 441998 2829 ns/op 6791 B/op 107 allocs/op
BenchmarkComplexMapDecodeStructAllTypes-16 179220 6359 ns/op 5300 B/op 130 allocs/op
BenchmarkComplexMapDecodeStructAllTypesParallel-16 412233 2933 ns/op 5310 B/op 130 allocs/op
BenchmarkComplexMapEncodeStructAllTypes-16 262464 4122 ns/op 4083 B/op 106 allocs/op
BenchmarkComplexMapEncodeStructAllTypesParallel-16 622110 2084 ns/op 4084 B/op 106 allocs/op
BenchmarkDecodeNestedStruct-16 823956 1247 ns/op 344 B/op 14 allocs/op
BenchmarkDecodeNestedStructParallel-16 4689418 267.5 ns/op 344 B/op 14 allocs/op
BenchmarkEncodeNestedStruct-16 1844667 636.0 ns/op 653 B/op 16 allocs/op
BenchmarkEncodeNestedStructParallel-16 4302678 278.8 ns/op 653 B/op 16 allocs/opCompetitor benchmarks can be found here
This package is aligned with the Go release policy in that support is guaranteed for the two most recent major versions.
This does not mean the package will not work with older versions of Go, only that we reserve the right to increase the MSGV(Minimum Supported Go Version) when the need arises to address Security issues/patches, OS issues & support or newly introduced functionality that would greatly benefit the maintenance and/or usage of this package.
If and when the MSGV is increased it will be done so in a minimum of a Minor release bump.
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.
- mold - Is a general library to help modify or set data within data structures and other objects.
Distributed under MIT License, please see license file in code for more details.