API reference / @node-ts/bus-messages / defineCommand

Function: defineCommand()

function defineCommand<TName>(name, options?): <TData>() => MessageDefinition<DefinedMessage<TName, TData>, TData>;

Defined in: packages/bus-messages/src/define-command.ts:29

Declares a command, an instruction sent to one handler, without writing a class. The definition creates commands from their fields, and is used anywhere a message class is: handlerFor, startedBy and when. The commands it creates are plain objects, with $name and $version added.

The name comes first and the fields second, so the name's literal type is inferred. Run bus generate-message-types (in @node-ts/bus-cli) to have Dates, Maps, Sets, bigints and classes in the fields restored when the command is received.

Type Parameters

Type Parameter
TName extends string

Parameters

Parameter	Type	Description
name	TName	the $name of the command, which routes it, so make it unique
options?	DefineMessageOptions	the $version of the command's contract

Returns

a function that takes the type of the command's fields as its type argument, and returns the definition

<TData>() => MessageDefinition<DefinedMessage<TName, TData>, TData>

Example

export const PlaceOrder = defineCommand('@my-org/orders/place-order')<{
  orderId: string
  placedAt: Date
}>()
export type PlaceOrder = MessageOf<typeof PlaceOrder>

await bus.send(PlaceOrder({ orderId: '1', placedAt: new Date() }))
handlerFor(PlaceOrder, async placeOrder => placeOrder.placedAt.getTime())