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47 lines
1.6 KiB
Markdown
47 lines
1.6 KiB
Markdown
# mapstructure [](https://godoc.org/github.com/mitchellh/mapstructure)
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mapstructure is a Go library for decoding generic map values to structures
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and vice versa, while providing helpful error handling.
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This library is most useful when decoding values from some data stream (JSON,
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Gob, etc.) where you don't _quite_ know the structure of the underlying data
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until you read a part of it. You can therefore read a `map[string]interface{}`
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and use this library to decode it into the proper underlying native Go
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structure.
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## Installation
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Standard `go get`:
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```
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$ go get github.com/mitchellh/mapstructure
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```
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## Usage & Example
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For usage and examples see the [Godoc](http://godoc.org/github.com/mitchellh/mapstructure).
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The `Decode` function has examples associated with it there.
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## But Why?!
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Go offers fantastic standard libraries for decoding formats such as JSON.
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The standard method is to have a struct pre-created, and populate that struct
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from the bytes of the encoded format. This is great, but the problem is if
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you have configuration or an encoding that changes slightly depending on
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specific fields. For example, consider this JSON:
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```json
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{
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"type": "person",
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"name": "Mitchell"
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}
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```
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Perhaps we can't populate a specific structure without first reading
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the "type" field from the JSON. We could always do two passes over the
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decoding of the JSON (reading the "type" first, and the rest later).
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However, it is much simpler to just decode this into a `map[string]interface{}`
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structure, read the "type" key, then use something like this library
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to decode it into the proper structure.
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