435c0d9fc8
This PR switches the Nomad repository from using govendor to Go modules for managing dependencies. Aspects of the Nomad workflow remain pretty much the same. The usual Makefile targets should continue to work as they always did. The API submodule simply defers to the parent Nomad version on the repository, keeping the semantics of API versioning that currently exists.
47 lines
1.6 KiB
Markdown
47 lines
1.6 KiB
Markdown
# mapstructure [](https://godoc.org/github.com/mitchellh/mapstructure)
|
|
|
|
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
|
|
|
|
Standard `go get`:
|
|
|
|
```
|
|
$ go get github.com/mitchellh/mapstructure
|
|
```
|
|
|
|
## Usage & Example
|
|
|
|
For usage and examples see the [Godoc](http://godoc.org/github.com/mitchellh/mapstructure).
|
|
|
|
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:
|
|
|
|
```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.
|