let producer = SignalProducer<String, NSError>(value: "testValue")

// Prints "producer started!"
producer.onStarting { () -> () in
    print("producer started!")
}.start()

// Prints "testValue"
producer.onNext { (object) -> () in
    print(object)
}.start()

// Prints "testValue", can be used to cast AnyObjects for example
producer.onNextAs { (string:String) -> () in
    print(string)
}.start()

// Prints "testValue", can be used to cast AnyObjects for example
producer.startWithNextAs { (string:String) -> () in
    print(string)
}

// Prints "Error Domain=sample.domain Code=-1 "(null)""
let errorProducer = SignalProducer<String, NSError>(error:NSError(domain: "sample.domain", code: -1, userInfo: nil))
errorProducer.onError { (error) -> () in
    print(error)
}.start()