# Ash.Signals ## signals Declare signals that resources can emit and listen to. ### Nested DSLs * [signal](#signals-signal) * argument ### Examples ``` signals do signal :post_created do argument :post_id, :uuid, allow_nil?: false end end ``` ### signals.signal ```elixir signal name ``` Declares a signal, and defines a struct for its arguments. For a signal named `:post_created` in `MyApp.Signals`, this is `MyApp.Signals.PostCreated`. ### Nested DSLs * [argument](#signals-signal-argument) ### Examples ``` signal :post_created do argument :post_id, :uuid, allow_nil?: false end ``` ### Arguments | Name | Type | Default | Docs | |------|------|---------|------| | [`name`](#signals-signal-name){: #signals-signal-name .spark-required} | `atom` | | The name of the signal. | ### Options | Name | Type | Default | Docs | |------|------|---------|------| | [`phase`](#signals-signal-phase){: #signals-signal-phase } | `:before_action \| :after_action \| :after_transaction` | `:after_action` | The phase of the emitting action during which the signal may be emitted. | | [`description`](#signals-signal-description){: #signals-signal-description } | `String.t` | | A description of the signal. | ### signals.signal.argument ```elixir argument name, type ``` An argument of the signal, provided by the emitter. ### Examples ``` argument :post_id, :uuid, allow_nil?: false ``` ### Arguments | Name | Type | Default | Docs | |------|------|---------|------| | [`name`](#signals-signal-argument-name){: #signals-signal-argument-name .spark-required} | `atom` | | The name of the field. | | [`type`](#signals-signal-argument-type){: #signals-signal-argument-type .spark-required} | `module` | | The type of the field. | ### Options | Name | Type | Default | Docs | |------|------|---------|------| | [`constraints`](#signals-signal-argument-constraints){: #signals-signal-argument-constraints } | `keyword` | `[]` | Constraints for the type. | | [`allow_nil?`](#signals-signal-argument-allow_nil?){: #signals-signal-argument-allow_nil? } | `boolean` | `true` | Whether the field may be `nil`. | | [`default`](#signals-signal-argument-default){: #signals-signal-argument-default } | `any` | | A default value for the field. | | [`description`](#signals-signal-argument-description){: #signals-signal-argument-description } | `String.t` | | A description of the field. | ### Introspection Target: `Ash.Signals.Field` ### Introspection Target: `Ash.Signals.Signal`