ExConstructor

ExConstructor is an Elixir library that makes it easy to instantiate structs from external data, such as that emitted by a JSON parser.

Add use ExConstructor after a defstruct statement to inject a constructor function into the module.

The generated constructor, called new by default, handles map-vs-keyword-list, string-vs-atom-keys, and camelCase-vs-under_score input data issues automatically, DRYing up your code and letting you move on to the interesting parts of your program.

Example

defmodule TestStruct do
  use ExConstructor
  defstruct field_one: nil,
            field_two: nil,
            field_three: nil,
            field_four: nil
end

TestStruct.new(%{"field_one" => "a", "fieldTwo" => "b", :field_three => "c", :FieldFour => "d"})
# => %TestStruct{field_one: "a", field_two: "b", field_three: "c", field_four: "d"}

Full Documentation

Full ExConstructor documentation is available on Hexdocs.pm.

Contributors

Many thanks to those who've contributed to ExConstructor:

• Graeme Coupar (@grambo)
• Mel Kicchi (@meowy)
• Andrey Ronin (@anronin)
• Eugene (@txssu)

How to Contribute

My favorite contributions are PRs with code that matches project style, and that come with full test coverage and documentation. I have a hard time saying no to them.

Feature requests are also welcome, but the timeline may be much longer.

Bug reports are great -- please include as much information as possible (Erlang/Elixir/Mix version, dependencies and their versions, minimal test case, etc.) and I will be much quicker in resolving the issue.

Authorship and License

ExConstructor is copyright 2016-2025 Appcues, Inc.

ExConstructor is released under the MIT License.