View Source Ecto.Type behaviour (Ecto v3.12.2)

Defines functions and the Ecto.Type behaviour for implementing basic custom types.

Ecto provides two types of custom types: basic types and parameterized types. Basic types are simple, requiring only four callbacks to be implemented, and are enough for most occasions. Parameterized types can be customized on the field definition and provide a wide variety of callbacks.

The definition of basic custom types and all of their callbacks are available in this module. You can learn more about parameterized types in Ecto.ParameterizedType. If in doubt, prefer to use basic custom types and rely on parameterized types if you need the extra functionality.

External vs internal vs database representation

The core functionality of a custom type is the mapping between external, internal and database representations of a value belonging to the type.

For a definition of external and internal data take a look at the related section in the changeset documentation.

stateDiagram-v2
  external: External Data
  internal: Internal Data
  database: Database Data
  external --> internal: cast/1
  external --> database: dump/1
  internal --> database: dump/1
  database --> internal: load/1

Example

Imagine you want to store a URI struct as part of a schema in a url-shortening service. There isn't an Ecto field type to support that value at runtime therefore a custom one is needed.

You also want to query not only by the full url, but for example by specific ports used. This is possible by putting the URI data into a map field instead of just storing the plain string representation.

from s in ShortUrl,
  where: fragment("?->>? ILIKE ?", s.original_url, "port", "443")

So the custom type does need to handle the conversion from external data to runtime data (cast/1) as well as transforming that runtime data into the :map Ecto native type and back (dump/1 and load/1).

defmodule EctoURI do
  use Ecto.Type
  def type, do: :map

  # Provide custom casting rules.
  # Cast strings into the URI struct to be used at runtime
  def cast(uri) when is_binary(uri) do
    {:ok, URI.parse(uri)}
  end

  # Accept casting of URI structs as well
  def cast(%URI{} = uri), do: {:ok, uri}

  # Everything else is a failure though
  def cast(_), do: :error

  # When loading data from the database, as long as it's a map,
  # we just put the data back into a URI struct to be stored in
  # the loaded schema struct.
  def load(data) when is_map(data) do
    data =
      for {key, val} <- data do
        {String.to_existing_atom(key), val}
      end
    {:ok, struct!(URI, data)}
  end

  # When dumping data to the database, we *expect* a URI struct
  # but any value could be inserted into the schema struct at runtime,
  # so we need to guard against them.
  def dump(%URI{} = uri), do: {:ok, Map.from_struct(uri)}
  def dump(_), do: :error
end

Now we can use our new field type above in our schemas:

defmodule ShortUrl do
  use Ecto.Schema

  schema "posts" do
    field :original_url, EctoURI
  end
end

Note: nil values are always bypassed and cannot be handled by custom types.

use Ecto.Type

When you use Ecto.Type, it will set @behaviour Ecto.Type and define default, overridable implementations for embed_as/1 and equal?/2.

Custom types and primary keys

Remember that, if you change the type of your primary keys, you will also need to change the type of all associations that point to said primary key.

Imagine you want to encode the ID so they cannot enumerate the content in your application. An Ecto type could handle the conversion between the encoded version of the id and its representation in the database. For the sake of simplicity, we'll use base64 encoding in this example:

defmodule EncodedId do
  use Ecto.Type

  def type, do: :id

  def cast(id) when is_integer(id) do
    {:ok, encode_id(id)}
  end
  def cast(_), do: :error

  def dump(id) when is_binary(id) do
    {:ok, id_decoded} = Base.decode64(id)
    {:ok, String.to_integer(id_decoded)}
  end

  def load(id) when is_integer(id) do
    {:ok, encode_id(id)}
  end

  defp encode_id(id) do
    id
    |> Integer.to_string()
    |> Base.encode64()
  end
end

To use it as the type for the id in our schema, we can use the @primary_key module attribute:

defmodule BlogPost do
  use Ecto.Schema

  @primary_key {:id, EncodedId, autogenerate: true}
  schema "posts" do
    belongs_to :author, Author, type: EncodedId
    field :content, :string
  end
end

defmodule Author do
  use Ecto.Schema

  @primary_key {:id, EncodedId, autogenerate: true}
  schema "authors" do
    field :name, :string
    has_many :posts, BlogPost
  end
end

The @primary_key attribute will tell ecto which type to use for the id.

Note the type: EncodedId option given to belongs_to in the BlogPost schema. By default, Ecto will treat associations as if their keys were :integers. Our primary keys are a custom type, so when Ecto tries to cast those ids, it will fail.

Alternatively, you can set @foreign_key_type EncodedId after @primary_key to automatically configure the type of all belongs_to fields.

Summary

Types

Custom types are represented by user-defined modules.

Primitive Ecto types (handled by Ecto).

t()

An Ecto type, primitive or custom.

Callbacks

Generates a loaded version of the data.

Casts the given input to the custom type.

Dumps the given term into an Ecto native type.

Dictates how the type should be treated inside embeds.

Checks if two terms are semantically equal.

Loads the given term into a custom type.

Returns the underlying schema type for the custom type.

Functions

Checks if the given atom can be used as base type.

Casts a value to the given type.

Casts a value to the given type or raises an error.

Checks if the given atom can be used as composite type.

Dumps a value to the given type.

Gets how the type is treated inside embeds for the given format.

Dumps the value for type considering it will be embedded in format.

Loads the value for type considering it was embedded in format.

Checks if two terms are equal.

Format type for error messaging and logs.

Checks if collection includes a term.

Loads a value with the given type.

Checks if a given type matches with a primitive type that can be found in queries.

Checks if the given type is parameterized by the given module.

Checks if we have a primitive type.

Retrieves the underlying schema type for the given, possibly custom, type.

Types

@type base() ::
  :integer
  | :float
  | :boolean
  | :string
  | :bitstring
  | :map
  | :binary
  | :decimal
  | :id
  | :binary_id
  | :utc_datetime
  | :naive_datetime
  | :date
  | :time
  | :any
  | :utc_datetime_usec
  | :naive_datetime_usec
  | :time_usec
  | :duration
@type composite() :: {:array, t()} | {:map, t()} | private_composite()
@type custom() :: module() | {:parameterized, {module(), term()}}

Custom types are represented by user-defined modules.

@type primitive() :: base() | composite()

Primitive Ecto types (handled by Ecto).

@type t() :: primitive() | custom()

An Ecto type, primitive or custom.

Callbacks

Link to this callback

autogenerate()

View Source (optional)
@callback autogenerate() :: term()

Generates a loaded version of the data.

This is callback is invoked when a custom type is given to field with the :autogenerate flag.

@callback cast(term()) :: {:ok, term()} | :error | {:error, keyword()}

Casts the given input to the custom type.

This callback is called on external input and can return any type, as long as the dump/1 function is able to convert the returned value into an Ecto native type. There are two situations where this callback is called:

  1. When casting values by Ecto.Changeset
  2. When passing arguments to Ecto.Query

You can return :error if the given term cannot be cast. A default error message of "is invalid" will be added to the changeset.

You may also return {:error, keyword()} to customize the changeset error message and its metadata. Passing a :message key, will override the default message. It is not possible to override the :type key.

For {:array, CustomType} or {:map, CustomType} the returned keyword list will be erased and the default error will be shown.

@callback dump(term()) :: {:ok, term()} | :error

Dumps the given term into an Ecto native type.

This callback is called with any term that was stored in the struct and it needs to validate them and convert it to an Ecto native type.

@callback embed_as(format :: atom()) :: :self | :dump

Dictates how the type should be treated inside embeds.

By default, the type is sent as itself, without calling dumping to keep the higher level representation. But it can be set to :dump so that it is dumped before being encoded.

@callback equal?(term(), term()) :: boolean()

Checks if two terms are semantically equal.

This callback is used for determining equality of types in Ecto.Changeset.

By default the terms are compared with the equal operator ==/2.

@callback load(term()) :: {:ok, term()} | :error

Loads the given term into a custom type.

This callback is called when loading data from the database and receives an Ecto native type. It can return any type, as long as the dump/1 function is able to convert the returned value back into an Ecto native type.

@callback type() :: t()

Returns the underlying schema type for the custom type.

For example, if you want to provide your own date structures, the type function should return :date.

Note this function is not required to return Ecto primitive types, the type is only required to be known by the adapter.

Functions

@spec base?(atom()) :: boolean()

Checks if the given atom can be used as base type.

iex> base?(:string)
true
iex> base?(:array)
false
iex> base?(Custom)
false
@spec cast(t(), term()) :: {:ok, term()} | {:error, keyword()} | :error

Casts a value to the given type.

cast/2 is used by the finder queries and changesets to cast outside values to specific types.

Note that nil can be cast to all primitive types as data stores allow nil to be set on any column.

NaN and infinite decimals are not supported, use custom types instead.

iex> cast(:any, "whatever")
{:ok, "whatever"}

iex> cast(:any, nil)
{:ok, nil}
iex> cast(:string, nil)
{:ok, nil}

iex> cast(:integer, 1)
{:ok, 1}
iex> cast(:integer, "1")
{:ok, 1}
iex> cast(:integer, "1.0")
:error

iex> cast(:id, 1)
{:ok, 1}
iex> cast(:id, "1")
{:ok, 1}
iex> cast(:id, "1.0")
:error

iex> cast(:float, 1.0)
{:ok, 1.0}
iex> cast(:float, 1)
{:ok, 1.0}
iex> cast(:float, "1")
{:ok, 1.0}
iex> cast(:float, "1.0")
{:ok, 1.0}
iex> cast(:float, "1-foo")
:error

iex> cast(:boolean, true)
{:ok, true}
iex> cast(:boolean, false)
{:ok, false}
iex> cast(:boolean, "1")
{:ok, true}
iex> cast(:boolean, "0")
{:ok, false}
iex> cast(:boolean, "whatever")
:error

iex> cast(:string, "beef")
{:ok, "beef"}
iex> cast(:binary, "beef")
{:ok, "beef"}

iex> cast(:decimal, Decimal.new("1.0"))
{:ok, Decimal.new("1.0")}
iex> cast(:decimal, "1.0bad")
:error

iex> cast({:array, :integer}, [1, 2, 3])
{:ok, [1, 2, 3]}
iex> cast({:array, :integer}, ["1", "2", "3"])
{:ok, [1, 2, 3]}
iex> cast({:array, :string}, [1, 2, 3])
:error
iex> cast(:string, [1, 2, 3])
:error

iex> cast(:utc_datetime, "2014-04-17T14:00:00Z")
{:ok, ~U[2014-04-17 14:00:00Z]}
iex> cast(:utc_datetime, "2014-04-17T14:00:00.030Z")
{:ok, ~U[2014-04-17 14:00:00Z]}
iex> cast(:utc_datetime, "2014-04-17T12:00:00-02:00")
{:ok, ~U[2014-04-17 14:00:00Z]}

Casts a value to the given type or raises an error.

See cast/2 for more information.

Examples

iex> Ecto.Type.cast!(:integer, "1")
1
iex> Ecto.Type.cast!(:integer, 1)
1
iex> Ecto.Type.cast!(:integer, nil)
nil

iex> Ecto.Type.cast!(:integer, 1.0)
** (Ecto.CastError) cannot cast 1.0 to :integer
@spec composite?(atom()) :: boolean()

Checks if the given atom can be used as composite type.

iex> composite?(:array)
true
iex> composite?(:string)
false
Link to this function

dump(type, value, dumper \\ &dump/2)

View Source
@spec dump(t(), term(), (t(), term() -> {:ok, term()} | :error)) ::
  {:ok, term()} | :error

Dumps a value to the given type.

Opposite to casting, dumping requires the returned value to be a valid Ecto type, as it will be sent to the underlying data store.

iex> dump(:string, nil)
{:ok, nil}
iex> dump(:string, "foo")
{:ok, "foo"}

iex> dump(:integer, 1)
{:ok, 1}
iex> dump(:integer, "10")
:error

iex> dump(:binary, "foo")
{:ok, "foo"}
iex> dump(:binary, 1)
:error

iex> dump({:array, :integer}, [1, 2, 3])
{:ok, [1, 2, 3]}
iex> dump({:array, :integer}, [1, "2", 3])
:error
iex> dump({:array, :binary}, ["1", "2", "3"])
{:ok, ["1", "2", "3"]}

Gets how the type is treated inside embeds for the given format.

See embed_as/1.

Link to this function

embedded_dump(type, value, format)

View Source

Dumps the value for type considering it will be embedded in format.

Examples

iex> Ecto.Type.embedded_dump(:decimal, Decimal.new("1"), :json)
{:ok, Decimal.new("1")}
Link to this function

embedded_load(type, value, format)

View Source

Loads the value for type considering it was embedded in format.

Examples

iex> Ecto.Type.embedded_load(:decimal, "1", :json)
{:ok, Decimal.new("1")}
Link to this function

equal?(type, term1, term2)

View Source
@spec equal?(t(), term(), term()) :: boolean()

Checks if two terms are equal.

Depending on the given type performs a structural or semantical comparison.

Examples

iex> equal?(:integer, 1, 1)
true
iex> equal?(:decimal, Decimal.new("1"), Decimal.new("1.00"))
true

Format type for error messaging and logs.

Link to this function

include?(type, term, collection)

View Source
@spec include?(t(), term(), Enum.t()) :: boolean()

Checks if collection includes a term.

Depending on the given type performs a structural or semantical comparison.

Examples

iex> include?(:integer, 1, 1..3)
true
iex> include?(:decimal, Decimal.new("1"), [Decimal.new("1.00"), Decimal.new("2.00")])
true
Link to this function

load(type, value, loader \\ &load/2)

View Source
@spec load(t(), term(), (t(), term() -> {:ok, term()} | :error)) ::
  {:ok, term()} | :error

Loads a value with the given type.

iex> load(:string, nil)
{:ok, nil}
iex> load(:string, "foo")
{:ok, "foo"}

iex> load(:integer, 1)
{:ok, 1}
iex> load(:integer, "10")
:error
Link to this function

match?(schema_type, query_type)

View Source
@spec match?(t(), primitive()) :: boolean()

Checks if a given type matches with a primitive type that can be found in queries.

iex> match?(:string, :any)
true
iex> match?(:any, :string)
true
iex> match?(:string, :string)
true

iex> match?({:array, :string}, {:array, :any})
true

iex> match?(Ecto.UUID, :uuid)
true
iex> match?(Ecto.UUID, :string)
false
Link to this function

parameterized?(arg1, module)

View Source
@spec parameterized?(t(), module()) :: boolean()

Checks if the given type is parameterized by the given module.

iex> type = Ecto.ParameterizedType.init(Ecto.Enum, values: [a: 1])
iex> Ecto.Type.parameterized?(type, Ecto.Enum)
true
iex> Ecto.Type.parameterized?(type, MyEnum)
false
@spec primitive?(t()) :: boolean()

Checks if we have a primitive type.

iex> primitive?(:string)
true
iex> primitive?(Another)
false

iex> primitive?({:array, :string})
true
iex> primitive?({:array, Another})
true
@spec type(t()) :: t()

Retrieves the underlying schema type for the given, possibly custom, type.

iex> type(:string)
:string
iex> type(Ecto.UUID)
:uuid

iex> type({:array, :string})
{:array, :string}
iex> type({:array, Ecto.UUID})
{:array, :uuid}

iex> type({:map, Ecto.UUID})
{:map, :uuid}