selectr

Select values from objects/arrays with key-path notation.

Key-path notation

Key-path notation is a simple format for describing how to traverse data structures. It's very similar to C languages, but with limitations. See the reference document for more information.

Usage

m := map[string]interface{}{
    "foo": map[string]interface{}{
        "bar": []interface{}{
            1,
            2,
            3,
        },
    },
}

sel, _ := selectr.Parse(".foo")
sel.Resolve(m) // => map[string]interface{}{"bar": []interface{}{1, 2, 3}}

sel, _ = selectr.Parse(".foo.bar")
sel.Resolve(m) // => []interface{}{1, 2, 3}

sel, _ = selectr.Parse(".foo.bar[1]")
sel.Resolve(m) // => 2

Use cases

• Referencing a dynamic value in a JSON/YAML file:

  Consider you maintain a program that allows users to reference arbitrary values, and one strategy of resolving a value is referencing a symbol in a JSON file.

  # example.json
  {
      "accounts": [{
          "id": 123,
          "name": "main"
      }]
  }

  The end-user references example.json with the selectr .accounts[0].name.

  jsonBytes, _ := os.Open(fileName)
  
  var m map[string]interface{}
  json.Unmarshal(jsonBytes, &m)
  
  sel, _ := selectr.Parse(selectrString)
  val := sel.Resolve(m)

  The val is resolved to "main".

• Import dynamic values from dynamic data files.