README.md (1678B)
1 # mapstructure [](https://godoc.org/github.com/mitchellh/mapstructure) 2 3 mapstructure is a Go library for decoding generic map values to structures 4 and vice versa, while providing helpful error handling. 5 6 This library is most useful when decoding values from some data stream (JSON, 7 Gob, etc.) where you don't _quite_ know the structure of the underlying data 8 until you read a part of it. You can therefore read a `map[string]interface{}` 9 and use this library to decode it into the proper underlying native Go 10 structure. 11 12 ## Installation 13 14 Standard `go get`: 15 16 ``` 17 $ go get github.com/mitchellh/mapstructure 18 ``` 19 20 ## Usage & Example 21 22 For usage and examples see the [Godoc](http://godoc.org/github.com/mitchellh/mapstructure). 23 24 The `Decode` function has examples associated with it there. 25 26 ## But Why?! 27 28 Go offers fantastic standard libraries for decoding formats such as JSON. 29 The standard method is to have a struct pre-created, and populate that struct 30 from the bytes of the encoded format. This is great, but the problem is if 31 you have configuration or an encoding that changes slightly depending on 32 specific fields. For example, consider this JSON: 33 34 ```json 35 { 36 "type": "person", 37 "name": "Mitchell" 38 } 39 ``` 40 41 Perhaps we can't populate a specific structure without first reading 42 the "type" field from the JSON. We could always do two passes over the 43 decoding of the JSON (reading the "type" first, and the rest later). 44 However, it is much simpler to just decode this into a `map[string]interface{}` 45 structure, read the "type" key, then use something like this library 46 to decode it into the proper structure.