defmodule Absinthe.Type.Union do
@moduledoc """
A unions is an abstract type made up of multiple possible concrete types.
No common fields are declared in a union. Compare to `Absinthe.Type.Interface`.
Because it's necessary for the union to determine the concrete type of a
resolved object, you must either:
* Provide a `:resolve_type` function on the union
* Provide a `:is_type_of` function on each possible concrete type
```
union :search_result do
description "A search result"
types [:person, :business]
resolve_type fn
%Person{}, _ -> :person
%Business{}, _ -> :business
end
end
```
"""
use Absinthe.Introspection.TypeKind, :union
alias Absinthe.{Schema, Type}
@typedoc """
* `:name` - The name of the union type. Should be a TitleCased `binary`. Set automatically.
* `:description` - A nice description for introspection.
* `:types` - The list of possible types.
* `:resolve_type` - A function used to determine the concrete type of a resolved object. See also `Absinthe.Type.Object`'s `:is_type_of`. Either `resolve_type` is specified in the union type, or every object type in the union must specify `is_type_of`
The `:resolve_type` function will be passed two arguments; the object whose type needs to be identified, and the `Absinthe.Execution` struct providing the full execution context.
The `__private__` and `:__reference__` keys are for internal use.
"""
@type t :: %__MODULE__{
name: binary,
description: binary,
types: [Type.identifier_t()],
identifier: atom,
fields: map,
__private__: Keyword.t(),
definition: module,
__reference__: Type.Reference.t()
}
defstruct name: nil,
description: nil,
identifier: nil,
resolve_type: nil,
types: [],
fields: nil,
__private__: [],
definition: nil,
__reference__: nil
@doc false
defdelegate functions, to: Absinthe.Blueprint.Schema.UnionTypeDefinition
@doc false
@spec member?(t, Type.t()) :: boolean
def member?(%{types: types}, %{identifier: ident}) do
ident in types
end
def member?(_, _) do
false
end
@doc false
@spec resolve_type(t, any, Absinthe.Resolution.t()) :: Type.t() | nil
def resolve_type(type, object, env, opts \\ [lookup: true])
def resolve_type(%{types: types} = union, obj, %{schema: schema} = env, opts) do
if resolver = Type.function(union, :resolve_type) do
case resolver.(obj, env) do
nil ->
nil
ident when is_atom(ident) ->
if opts[:lookup] do
Absinthe.Schema.lookup_type(schema, ident)
else
ident
end
end
else
type_name =
Enum.find(types, fn
%{is_type_of: nil} ->
false
type ->
type = Absinthe.Schema.lookup_type(schema, type)
Absinthe.Type.function(type, :is_type_of).(obj)
end)
if opts[:lookup] do
Schema.lookup_type(schema, type_name)
else
type_name
end
end
end
end