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Published: Feb 9, 2021 License: Apache-2.0 Imports: 9 Imported by: 0



Package mapstructure exposes functionality to convert an arbitrary map[string]interface{} into a native Go structure.

The Go structure can be arbitrarily complex, containing slices, other structs, etc. and the decoder will properly decode nested maps and so on into the proper structures in the native Go struct. See the examples to see what the decoder is capable of.



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func Decode

func Decode(input interface{}, output interface{}) error

Decode takes an input structure and uses reflection to translate it to the output structure. output must be a pointer to a map or struct.

func DecodeHookExec

func DecodeHookExec(
	raw DecodeHookFunc,
	from reflect.Type, to reflect.Type,
	data interface{}) (interface{}, error)

DecodeHookExec executes the given decode hook. This should be used since it'll naturally degrade to the older backwards compatible DecodeHookFunc that took reflect.Kind instead of reflect.Type.

func DecodeMetadata

func DecodeMetadata(input interface{}, output interface{}, metadata *Metadata) error

DecodeMetadata is the same as Decode, but is shorthand to enable metadata collection. See DecoderConfig for more info.

func WeakDecode

func WeakDecode(input, output interface{}) error

WeakDecode is the same as Decode but is shorthand to enable WeaklyTypedInput. See DecoderConfig for more info.

func WeakDecodeMetadata

func WeakDecodeMetadata(input interface{}, output interface{}, metadata *Metadata) error

WeakDecodeMetadata is the same as Decode, but is shorthand to enable both WeaklyTypedInput and metadata collection. See DecoderConfig for more info.

func WeaklyTypedHook

func WeaklyTypedHook(
	f reflect.Kind,
	t reflect.Kind,
	data interface{}) (interface{}, error)

WeaklyTypedHook is a DecodeHookFunc which adds support for weak typing to the decoder.

Note that this is significantly different from the WeaklyTypedInput option of the DecoderConfig.


type DecodeHookFunc

type DecodeHookFunc interface{}

DecodeHookFunc is the callback function that can be used for data transformations. See "DecodeHook" in the DecoderConfig struct.

The type should be DecodeHookFuncType or DecodeHookFuncKind. Either is accepted. Types are a superset of Kinds (Types can return Kinds) and are generally a richer thing to use, but Kinds are simpler if you only need those.

The reason DecodeHookFunc is multi-typed is for backwards compatibility: we started with Kinds and then realized Types were the better solution, but have a promise to not break backwards compat so we now support both.

func ComposeDecodeHookFunc

func ComposeDecodeHookFunc(fs ...DecodeHookFunc) DecodeHookFunc

ComposeDecodeHookFunc creates a single DecodeHookFunc that automatically composes multiple DecodeHookFuncs.

The composed funcs are called in order, with the result of the previous transformation.

func StringToIPHookFunc

func StringToIPHookFunc() DecodeHookFunc

StringToIPHookFunc returns a DecodeHookFunc that converts strings to net.IP

func StringToIPNetHookFunc

func StringToIPNetHookFunc() DecodeHookFunc

StringToIPNetHookFunc returns a DecodeHookFunc that converts strings to net.IPNet

func StringToSliceHookFunc

func StringToSliceHookFunc(sep string) DecodeHookFunc

StringToSliceHookFunc returns a DecodeHookFunc that converts string to []string by splitting on the given sep.

func StringToTimeDurationHookFunc

func StringToTimeDurationHookFunc() DecodeHookFunc

StringToTimeDurationHookFunc returns a DecodeHookFunc that converts strings to time.Duration.

func StringToTimeHookFunc

func StringToTimeHookFunc(layout string) DecodeHookFunc

StringToTimeHookFunc returns a DecodeHookFunc that converts strings to time.Time.

type DecodeHookFuncKind

type DecodeHookFuncKind func(reflect.Kind, reflect.Kind, interface{}) (interface{}, error)

DecodeHookFuncKind is a DecodeHookFunc which knows only the Kinds of the source and target types.

type DecodeHookFuncType

type DecodeHookFuncType func(reflect.Type, reflect.Type, interface{}) (interface{}, error)

DecodeHookFuncType is a DecodeHookFunc which has complete information about the source and target types.

type Decoder

type Decoder struct {
	// contains filtered or unexported fields

A Decoder takes a raw interface value and turns it into structured data, keeping track of rich error information along the way in case anything goes wrong. Unlike the basic top-level Decode method, you can more finely control how the Decoder behaves using the DecoderConfig structure. The top-level Decode method is just a convenience that sets up the most basic Decoder.

func NewDecoder

func NewDecoder(config *DecoderConfig) (*Decoder, error)

NewDecoder returns a new decoder for the given configuration. Once a decoder has been returned, the same configuration must not be used again.

func (*Decoder) Decode

func (d *Decoder) Decode(input interface{}) error

Decode decodes the given raw interface to the target pointer specified by the configuration.

type DecoderConfig

type DecoderConfig struct {
	// DecodeHook, if set, will be called before any decoding and any
	// type conversion (if WeaklyTypedInput is on). This lets you modify
	// the values before they're set down onto the resulting struct.
	// If an error is returned, the entire decode will fail with that
	// error.
	DecodeHook DecodeHookFunc

	// If ErrorUnused is true, then it is an error for there to exist
	// keys in the original map that were unused in the decoding process
	// (extra keys).
	ErrorUnused bool

	// ZeroFields, if set to true, will zero fields before writing them.
	// For example, a map will be emptied before decoded values are put in
	// it. If this is false, a map will be merged.
	ZeroFields bool

	// If WeaklyTypedInput is true, the decoder will make the following
	// "weak" conversions:
	//   - bools to string (true = "1", false = "0")
	//   - numbers to string (base 10)
	//   - bools to int/uint (true = 1, false = 0)
	//   - strings to int/uint (base implied by prefix)
	//   - int to bool (true if value != 0)
	//   - string to bool (accepts: 1, t, T, TRUE, true, True, 0, f, F,
	//     FALSE, false, False. Anything else is an error)
	//   - empty array = empty map and vice versa
	//   - negative numbers to overflowed uint values (base 10)
	//   - slice of maps to a merged map
	//   - single values are converted to slices if required. Each
	//     element is weakly decoded. For example: "4" can become []int{4}
	//     if the target type is an int slice.
	WeaklyTypedInput bool

	// Metadata is the struct that will contain extra metadata about
	// the decoding. If this is nil, then no metadata will be tracked.
	Metadata *Metadata

	// Result is a pointer to the struct that will contain the decoded
	// value.
	Result interface{}

	// The tag name that mapstructure reads for field names. This
	// defaults to "mapstructure"
	TagName string

DecoderConfig is the configuration that is used to create a new decoder and allows customization of various aspects of decoding.

type Error

type Error struct {
	Errors []string

Error implements the error interface and can represents multiple errors that occur in the course of a single decode.

func (*Error) Error

func (e *Error) Error() string

func (*Error) WrappedErrors

func (e *Error) WrappedErrors() []error

WrappedErrors implements the errwrap.Wrapper interface to make this return value more useful with the errwrap and go-multierror libraries.

type Metadata

type Metadata struct {
	// Keys are the keys of the structure which were successfully decoded
	Keys []string

	// Unused is a slice of keys that were found in the raw value but
	// weren't decoded since there was no matching field in the result interface
	Unused []string

Metadata contains information about decoding a structure that is tedious or difficult to get otherwise.

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