Categorygithub.com/go-viper/mapstructure/v2
modulepackage
2.2.1
Repository: https://github.com/go-viper/mapstructure.git
Documentation: pkg.go.dev
Overview
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13
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# README

mapstructure

GitHub Workflow Status go.dev reference Go Version

mapstructure is a Go library for decoding generic map values to structures and vice versa, while providing helpful error handling.

This library is most useful when decoding values from some data stream (JSON, Gob, etc.) where you don't quite know the structure of the underlying data until you read a part of it. You can therefore read a map[string]interface{} and use this library to decode it into the proper underlying native Go structure.

Installation

go get github.com/go-viper/mapstructure/v2

Migrating from github.com/mitchellh/mapstructure

@mitchehllh announced his intent to archive some of his unmaintained projects (see here and here). This is a repository achieved the "blessed fork" status.

You can migrate to this package by changing your import paths in your Go files to github.com/go-viper/mapstructure/v2. The API is the same, so you don't need to change anything else.

Here is a script that can help you with the migration:

sed -i 's/github.com\/mitchellh\/mapstructure/github.com\/go-viper\/mapstructure\/v2/g' $(find . -type f -name '*.go')

If you need more time to migrate your code, that is absolutely fine.

Some of the latest fixes are backported to the v1 release branch of this package, so you can use the Go modules replace feature until you are ready to migrate:

replace github.com/mitchellh/mapstructure => github.com/go-viper/mapstructure v1.6.0

Usage & Example

For usage and examples see the documentation.

The Decode function has examples associated with it there.

But Why?!

Go offers fantastic standard libraries for decoding formats such as JSON. The standard method is to have a struct pre-created, and populate that struct from the bytes of the encoded format. This is great, but the problem is if you have configuration or an encoding that changes slightly depending on specific fields. For example, consider this JSON:

{
  "type": "person",
  "name": "Mitchell"
}

Perhaps we can't populate a specific structure without first reading the "type" field from the JSON. We could always do two passes over the decoding of the JSON (reading the "type" first, and the rest later). However, it is much simpler to just decode this into a map[string]interface{} structure, read the "type" key, then use something like this library to decode it into the proper structure.

Credits

Mapstructure was originally created by @mitchellh. This is a maintained fork of the original library.

Read more about the reasons for the fork here.

License

The project is licensed under the MIT License.

# Functions

ComposeDecodeHookFunc creates a single DecodeHookFunc that automatically composes multiple DecodeHookFuncs.
Decode takes an input structure and uses reflection to translate it to the output structure.
DecodeHookExec executes the given decode hook.
DecodeMetadata is the same as Decode, but is shorthand to enable metadata collection.
NewDecoder returns a new decoder for the given configuration.
OrComposeDecodeHookFunc executes all input hook functions until one of them returns no error.
No description provided by the author
StringToBasicTypeHookFunc returns a DecodeHookFunc that converts strings to basic types.
StringToBoolHookFunc returns a DecodeHookFunc that converts strings to bool.
StringToByteHookFunc returns a DecodeHookFunc that converts strings to byte.
StringToComplex128HookFunc returns a DecodeHookFunc that converts strings to complex128.
StringToComplex64HookFunc returns a DecodeHookFunc that converts strings to complex64.
StringToFloat32HookFunc returns a DecodeHookFunc that converts strings to float32.
StringToFloat64HookFunc returns a DecodeHookFunc that converts strings to float64.
StringToInt16HookFunc returns a DecodeHookFunc that converts strings to int16.
StringToInt32HookFunc returns a DecodeHookFunc that converts strings to int32.
StringToInt64HookFunc returns a DecodeHookFunc that converts strings to int64.
StringToInt8HookFunc returns a DecodeHookFunc that converts strings to int8.
StringToIntHookFunc returns a DecodeHookFunc that converts strings to int.
StringToIPHookFunc returns a DecodeHookFunc that converts strings to net.IP.
StringToIPNetHookFunc returns a DecodeHookFunc that converts strings to net.IPNet.
StringToNetIPAddrHookFunc returns a DecodeHookFunc that converts strings to netip.Addr.
StringToNetIPAddrPortHookFunc returns a DecodeHookFunc that converts strings to netip.AddrPort.
StringToRuneHookFunc returns a DecodeHookFunc that converts strings to rune.
StringToSliceHookFunc returns a DecodeHookFunc that converts string to []string by splitting on the given sep.
StringToTimeDurationHookFunc returns a DecodeHookFunc that converts strings to time.Duration.
StringToTimeHookFunc returns a DecodeHookFunc that converts strings to time.Time.
StringToUint16HookFunc returns a DecodeHookFunc that converts strings to uint16.
StringToUint32HookFunc returns a DecodeHookFunc that converts strings to uint32.
StringToUint64HookFunc returns a DecodeHookFunc that converts strings to uint64.
StringToUint8HookFunc returns a DecodeHookFunc that converts strings to uint8.
StringToUintHookFunc returns a DecodeHookFunc that converts strings to uint.
StringToURLHookFunc returns a DecodeHookFunc that converts strings to *url.URL.
TextUnmarshallerHookFunc returns a DecodeHookFunc that applies strings to the UnmarshalText function, when the target type implements the encoding.TextUnmarshaler interface.
WeakDecode is the same as Decode but is shorthand to enable WeaklyTypedInput.
WeakDecodeMetadata is the same as Decode, but is shorthand to enable both WeaklyTypedInput and metadata collection.
WeaklyTypedHook is a DecodeHookFunc which adds support for weak typing to the decoder.

# Structs

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.
DecoderConfig is the configuration that is used to create a new decoder and allows customization of various aspects of decoding.
Metadata contains information about decoding a structure that is tedious or difficult to get otherwise.

# Interfaces

DecodeHookFunc is the callback function that can be used for data transformations.

# Type aliases

DecodeHookFuncKind is a DecodeHookFunc which knows only the Kinds of the source and target types.
DecodeHookFuncType is a DecodeHookFunc which has complete information about the source and target types.
DecodeHookFuncValue is a DecodeHookFunc which has complete access to both the source and target values.