validate_each.ex

@doc """
Validate each array element with validator

Examples
  iex> changeset
  ...> |> validate_each(:emails, &validate_email)
  ...> |> validate_each(:phones, &validate_format(&1, &2, ~r/\d+/))
  ...> |> validate_each(:phones, &validate_length/3, is: 4)
"""
def validate_each(changeset, field, validator, opts) do
  validate_each(changeset, field, & apply(validator, [&1,&2,opts]))
end

def validate_each(changeset, field, validator) do
  %{changes: changes, errors: errors} = changeset

  new = case Map.get(changes, field) do
    nil -> []
    values -> Enum.flat_map values, fn value ->
      # since validators work only on single fields we need to trick them
      single_changeset = %Ecto.Changeset{changes: %{field => value}, errors: []}
      validator.(single_changeset, field).errors
    end
  end

  case new do
    []    -> changeset
    [_|_] -> %{changeset | errors: new ++ errors, valid?: false}
  end
end