Attributes specify the name, type and properties of a piece of information in a resource.
There are two ways to write an attribute:
attribute :name, :string, allow_nil?: false # or ... attribute :name, :string do allow_nil? false end
Both ways will work. Though when you’re using many options the latter is preferred. This is also true of any other keyword in the Ash DSL, so you can build a flexible yet concise domain model.
For more information on attribute types including composite types and defining your own custom type see
You can find a comprehensive of attribute options with detailed descriptions on the
In Ash there are 4 special attributes these are:
These are really just shorthand for an attribute with specific options set. They’re outlined below.
You may recognise this if you have used Ecto before. This attribute will record the time at which each row is created, by default it uses
create_timestamp :inserted_at is equivalent to an attribute with these options:
attribute :inserted_at, :utc_datetime_usec do writeable? false private? true default &DateTime.utc_now/0 match_other_defaults? true allow_nil? false end
This is also similar in Ecto. This attribute records the last time a row was updated, also using
DateTime.utc_now/1 by default.
update_timestamp :updated_at is equivalent to:
attribute :updated_at, :utc_datetime_usec do writeable? false private? true default &DateTime.utc_now/0 updated_default &DateTime.utc_now/0 match_other_defaults? true allow_nil? false end
This attribute is used in almost every resource. It generates a UUID every time a new record is made.
uuid_primary_key :id is equivalent to:
attribute :id, :uuid do writeable? false default &Ash.UUID.generate/0 primary_key? true allow_nil? false end
Don’t use this attribute unless absolutely necessary, there are a lot of good reasons to not use autoincrementing integer ids . If you do, please make sure these resource are only accessed internally and aren’t exposed via a public API.
integer_primary_key :id is equivalent to:
attribute :id, :integer do writeable? false generated? true primary_key? true allow_nil? false end