 		return NSError(domain: "RACAction", code: 1, userInfo: nil)
 	}
 
+	let _scheduler: Scheduler
 	let _execute: I -> Promise<Result<O>>
 	let _executions = SignalingProperty<ExecutionSignal?>(nil)
 


	/// Initializes an action that will be conditionally enabled, and create
	/// a Promise for each execution.
	init(enabledIf: Signal<Bool>, execute: I -> Promise<Result<O>>) {
		_execute = execute

		enabled = .constant(true)
		enabled = enabledIf

	}

	/// Initializes an action that will create a Promise for each execution.
	convenience init(scheduler: Scheduler = MainScheduler(), execute: I -> Promise<Result<O>>) {
		self.init(enabledIf: .constant(true), scheduler: scheduler, execute: execute)
	}

	/// Executes the action on the main thread with the given input.
