handleCommandWithDecider

@delta-base/toolkit

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Function: handleCommandWithDecider()

handleCommandWithDecider<State, TCommand, TEvent>(eventStore, streamId, command, decider, options?): Promise<CommandHandlerResult<State, TEvent>>

Creates a command handler with Decider pattern

Steps:

1. Aggregate the stream to get current state
2. Run business logic using Decider.decide function
3. Append events to stream
4. Return result with new state and events

Type Parameters

State

State

TCommand

TCommand extends Command

TEvent

TEvent extends Readonly<{ data: EventData; metadata?: PlatformEventMetadata; type: string; }> = Readonly<{ data: EventData; metadata?: PlatformEventMetadata; type: string; }>

Parameters

eventStore

EventStore

The event store instance

streamId

string

The stream identifier

command

TCommand

The command to handle

decider

Decider<State, TCommand, TEvent>

The decider implementation with decide, evolve, and initialState

options?

DeciderCommandHandlerOptions

Optional command handler options

Returns

Promise<CommandHandlerResult<State, TEvent>>

Promise resolving to command handler result with new state and events

Example

const result = await handleCommandWithDecider(
  eventStore,
  'user-123',
  { type: 'RegisterUser', data: { userId: '123' } },
  {
    decide: (state, cmd) => [{ type: 'UserRegistered', data: cmd.data }],
    evolve: (state, event) => ({ ...state, registered: true }),
    initialState: () => ({ registered: false })
  }
);