Implementing ActiveRecords’ errors full_messages for Elixir/Phoenix and Ecto

In Rails you can easily get an array of full error messages from a model.

full_messages (ActiveModel::Errors) - APIdock

class Person
  validates_presence_of :name, :address, :email
  validates_length_of :name, in: 5..30
end

person = Person.create(address: '123 First St.')
person.errors.full_messages
# => ["Name is too short (minimum is 5 characters)", "Name can't be blank", "Email can't be blank"]

Here’s how I did it for my Phoenix project with Ecto.

def save_torrent(torrent) do
  changeset = Torrent.changeset(%Torrent{}, torrent)
  case Repo.insert(changeset) do
    {:ok, _torrent} ->
      Logger.info "Torrent saved to database: #{torrent.name}"
    {:error, changeset} ->
      errors = Enum.reduce(changeset.errors, [], fn (field_error, errors) ->
        {field, {error_message, _}} = field_error
        errors = ["#{field} #{error_message}" | errors]
      end)
      Logger.error "Torrent skipped: #{torrent.name} - Errors: #{Enum.join(errors, ", ")}"
  end
end

We iterate through a changeset’s errors map and reduce each one into a errors accumulator.

Here’s the relevant code:

errors = Enum.reduce(changeset.errors, [], fn (field_error, errors) ->
  {field, {error_message, _}} = field_error
  errors = ["#{field} #{error_message}" | errors]
end)

Update: Jose suggested a cleaner option! Check it out.

errors = for {key, {message, _}} <- changeset.errors do
  "#{key} #{message}"
end

errors ends up being a list of strings, which we can just Enum.join() to turn it into a nice comma separated string.

[error] Torrent skipped: Big Bunny - Errors: magnet has already been taken

Hopefully we can build this method directly into Ecto so in the future we can just call:

changeset.full_errors

Please leave your feedback on the feature proposal:

New feature proposal: changeset errors full message.

Implementing ActiveRecords’ errors full_messages for Elixir/Phoenix and Ecto was originally published in sergiotapia on Medium, where people are continuing the conversation by highlighting and responding to this story.