Represents a struct.

Use the instance_of constraint to specify that it must be an instance of a specific struct.

This cannot be loaded from a database unless the instance_of constraint is provided. If not, it can only be used to cast input, i.e for arguments.

Alternative: Ash.TypedStruct

For simpler use cases where you want to define a struct with typed fields inline, consider using Ash.TypedStruct. It provides a DSL for defining structs with:

• Field type specifications and constraints
• Default values
• Required fields (via allow_nil?: false)
• Automatic new/1 and new!/1 functions

Example:

defmodule MyStruct do
  use Ash.TypedStruct
  typed_struct do
    field :name, :string, allow_nil?: false
    field :age, :integer, constraints: [min: 0]
    field :email, :string, default: nil
  end
end

Ash.TypedStruct automatically creates an Ash.Type.Struct with the appropriate constraints under the hood.

Constraints

• :instance_of (atom/0) - The module the struct should be an instance of

• :preserve_nil_values? (boolean/0) - If set to true, when storing, nil values will be kept. Otherwise, nil values will be omitted. The default value is false.

• :fields (keyword/0) - The types of the fields in the struct, and their constraints.
  For example:

  fields:  [
    amount: [
      type: :integer,
      description: "The amount of the transaction",
      constraints: [
        max: 10
      ]
    ],
    currency: [
      type: :string,
      allow_nil?: false,
      description: "The currency code of the transaction",
      constraints: [
        max_length: 3
      ]
    ]
  ]  

  allow_nil? is true by default

  • :type (an Ash.Type) - Required.

  • :allow_nil? (boolean/0) - The default value is true.

  • :description (String.t/0)

  • :constraints (keyword/0) - The default value is [].