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AFSM

@ChangeState

Signature

function ChangeState(
  from: string | string[],
  to: string,
  opt?: ChangeOption
): (target: any, propertyKey: string | symbol, descriptor: TypedPropertyDescriptor<any>) => void

Parameters

from: string | string[]

Allowed starting state(s).

ValueMeaning
'idle'only 'idle'
['a', 'b']either 'a' or 'b'
FSM.INITi.e. '[*]', the initial state
[] (empty)any state, and aborts an in-flight MiddleState

On mismatch, throws FSMError:

{className} {action} to {to} failed: current state {state} not from {from}

to: string

Target state. The stable state after a successful transition.

opt?: ChangeOption

See ChangeOption.

Decorated behavior

The decorated method is replaced with this flow:

  1. If opt.context is set, fsm = FSM.get(context) (composition mode)
  2. If already in to: return immediately (async: Promise.resolve(cached), sync: cached)
  3. If currently in a MiddleState matching opt.abortAction: call middle.abort(fsm)
  4. Validate from; on mismatch return the error (reject / throw / return, depending on ignoreError and sync)
  5. Create MiddleState(old, to, action) and call setState(middle) (enter intermediate)
  6. Run the original method
    • Returns Promise: .then(success).catch(failed)
    • Returns sync value: success(result) (async wraps Promise.resolve, sync returns directly)
  7. success: cache result; if not aborted, setState(to); trigger opt.success
  8. failed: setState(old, err); trigger opt.fail; return the error

stateDiagram metadata

When applied, @ChangeState registers {from, to, action} metadata in the module-level stateDiagram Map (only when opt.context is not set), for the FSM.prototype.stateDiagram getter to generate mermaid edges.

Example

class Conn extends FSM {
  @ChangeState(FSM.INIT, 'connected', {
    action: 'connect',
    success: (r) => console.log('connected'),
    fail: (e) => console.error(e)
  })
  async connect() {
    return await api()
  }
}

See also