EctoNestedChangeset

This is a package for manipulating nested Ecto changesets.

Installation

Add ecto_nested_changeset to your list of dependencies in mix.exs:

def deps do
  [
    {:ecto_nested_changeset, "~> 1.1.0"}
  ]
end

This package is tested against the Elixir and OTP versions that are still supported upstream. Older versions down to the requirement in mix.exs may still work, but they are not covered by CI and not officially supported.

Usage

The primary use case of this library is the manipulation of Ecto changesets used as a source for dynamic, nested forms in Phoenix LiveView.

category = %Category{
  posts: [
    %Post{
      id: 1,
      comments: [
        %Comment{body: "potato", id: 1},
        %Comment{body: "you", id: 2}
      ],
      title: "must"
    },
    %Post{comments: [], id: 2, title: "young"}
  ]
}

category
|> Ecto.Changeset.change()
|> append_at(:posts, %Post{title: "Padawan", comments: []})
|> prepend_at([:posts, 0, :comments], %Comment{body: "ecneitaP"})
|> delete_at([:posts, 0, :comments, 1], mode: {:action, :delete})
|> insert_at([:posts, 1], %Post{title: "have"})
|> append_at([:posts, 2, :comments], %Comment{body: "my"})
|> update_at([:posts, 0, :comments, 0, :body], &String.reverse/1)
|> Ecto.Changeset.apply_changes()

%Category{
  posts: [
    %Post{
      comments: [
        %Comment{body: "Patience"},
        %Comment{body: "you", id: 2}
      ],
      id: 1,
      title: "must"
    },
    %Post{title: "have"},
    %Post{
      comments: [%Comment{body: "my"}],
      id: 2,
      title: "young"
    },
    %Post{title: "Padawan"}
  ]
}

Alternatives

Since Ecto 3.10, Ecto.Changeset.cast_assoc/3 and Ecto.Changeset.cast_embed/3 take :sort_param and :drop_param, which add, remove and reorder items from the form parameters while casting. If that is all you need, you should prefer those functions.

This library works on a changeset that already exists, rather than on the parameters one is built from. It covers array fields and the cases where you are not casting parameters at all.

Example application

There is an example Phoenix application with a dynamic nested LiveView form in the /example folder of the repository.

git clone https://github.com/woylie/ecto_nested_changeset.git
cd ecto_nested_changeset/example
mix setup
mix phx.server

Note that Postgres needs to be running to use the application.

You can access the application at http://localhost:4000.

Status

This library is actively maintained, but given its narrow purpose, it will not see frequent updates.