/* 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. - 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 `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. Mixing array/slice with array[idx]/slice[idx], in which order are they parsed? array/slice then array[idx]/slice[idx] 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
Example example decoding the above HTML 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"}, } } example 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) } Registering Custom Types 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{}) Ignoring Fields you can tell form to ignore fields using `-` in the tag type MyStruct struct { Field string `form:"-"` } Omitempty 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"` } 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"} */ package form