Domo.Changeset (Domo v1.5.18) View Source

Validation functions for Ecto.Changeset.

The Ecto schema changes can be validated to conform to types in t() and to fulfill appropriate preconditions.

defmodule User do
  use Ecto.Schema
  use Domo, :changeset

  import Ecto.Changeset
  import Domo.Changeset

  schema "users" do
    field :first_name, :string
    field :last_name, :string
    field :age, :integer
    has_many(:addresses, Address)
  end

  @type t :: %__MODULE__{
    first_name :: String.t() | nil,
    last_name :: String.t(),
    age :: age()
    addresses :: Schema.has_many(Address)
  }

  @type age :: pos_integer()
  precond age: &validate_age/1

  @max_age 150
  defp validate_age(age) when age < @max_age, do: :ok
  defp validate_age(_age), do: {:error, "age should be in 1..#{@max_age}"}

  def changeset(user, attrs) do
    user
    |> cast(attrs, __schema__(:fields))
    |> validate_type(maybe_filter_precond_errors: true)
    |> cast_assoc(:addresses)
  end
end

The skip_defaults: true option disables the validation of defaults to match to t() type at compile time. That is useful because any Ecto schema has all fields set to nil by default.

The first_name field is not required to have a value in the changeset because it has nil as one of the possible types defined.

validate_type/2 function automatically adds type ensurance errors to the changeset. The maybe_filter_precond_errors: true option enables the filtering of the precondition error message for :age field. That error is ready to be communicated to the user.

Link to this section Summary

Functions

validate_schemaless_type(changeset, struct, opts \\ [])

Validates schemaless changeset changes to conform to the schema's t() type and fulfill preconditions.

validate_type(changeset, opts \\ [])

Validates changeset changes except for assoc fields to conform to the schema's t() type and fulfill preconditions.

Link to this section Functions

validate_schemaless_type(changeset, struct, opts \\ [])

Validates schemaless changeset changes to conform to the schema's t() type and fulfill preconditions.

Similar to validate_type/2.

struct is a module name providing t() type and preconditions for changes validation.

Examples

{%{}, %{first_name: :string, last_name: :string, age: :integer}}
|> change(%{last_name: "Doe", age: 21})
|> validate_schemaless_type(User)

validate_type(changeset, opts \\ [])

Validates changeset changes except for assoc fields to conform to the schema's t() type and fulfill preconditions.

Adds error to the changeset for any missing field value required by t() type.

In case there's at least one error, the list of errors will be appended to the :errors field of the changeset and the :valid? flag will be set to false.

The function doesn't check for missing value or mismatching type of the fields having the following Ecto.Schema types in t(): belongs_to(t), has_one(t), has_many(t), many_to_many(t), embeds_one(t), and embeds_many(t). Use Ecto.Changeset.cast_assoc/2 or Ecto.Changeset.cast_embed/3 explicitly to delegate the validation to appropriate changeset function. And pass :required option if the field with nested changeset is required.

The function raises a RuntimeError if some of the changed fields are not defined in the t() type.

Options

:fields - the list of changed fields that should be validated
:maybe_filter_precond_errors - when set to true the function returns first error received from the precondition function for each field. In case if no precondition function is defined for the field type, then autogenerated error will be returned.
:take_error_fun - function returning most relevant error from the list of errors for a field. Works when maybe_filter_precond_errors: true is given. It can be useful in cases when several precondition errors are returned for the given field. By default it's fn list -> List.first(list) end.

Examples

%User{}
|> cast(%{last_name: "Doe", age: 21, comments: [%{message: "hello"}]}, [:last_name, :age])
|> validate_type()
|> cast_assoc(:comments)