Operations.swift

gistfile1.swift

class Promise<T> {
	var value : T? {
		didSet {
			if let value = value {
				notifyListeners(value)
			}
		}
	}
	
	init(value : T? = nil) {
		self.value = value
	}
	
	func getValue() -> T {
		let sem = dispatch_semaphore_create(0)
		waitForValue { _ in }
		dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER)
		return value!
	}
	
	var listeners : [T -> Void] = []
	
	func waitForValue(completion : T -> Void) {
		listeners.append(completion)
	}
	
	func notifyListeners(value : T) {
		for listener in listeners {
			listener(value)
		}
	}
}

protocol Operation {
	typealias Input
	typealias Output
	
	var input : Promise<Input>? { get set }
	var output : Promise<Output> { get }
}

infix operator >>> {
associativity left
}

func >>><T : Operation, U : Operation where T.Output == U.Input>(lhs : T, rhs : U) -> CompositeOperation<T.Output> {
	return CompositeOperation(input: lhs.output, output: rhs.input!)
}

func >>><T, U : Operation where T == U.Input>(lhs : Promise<T>, rhs : U) -> CompositeOperation<T> {
	return CompositeOperation(input: lhs, output: rhs.input!)
}

class CompositeOperation<T> : Operation {
	typealias Input = T
	typealias Output = T
	
	var input : Promise<Input>? {
		didSet {
			if let input = input?.getValue() {
				output.value = input
			}
		}
	}
	
	var output = Promise<Output>()
	
	init(input : Promise<T>, output : Promise<T>) {
		self.input = input
		self.output = output
	}
}

@objc protocol NetworkOperationDelegate {
	func didMakeProgress(progess : CGFloat)
}

class NetworkOperation : Operation {
	typealias Input = NSURL
	typealias Output = NSData
	
	var input : Promise<Input>? {
		didSet {
			if let input = input?.getValue() {
				begin(input)
			}
		}
	}
	
	var output = Promise<Output>()
	
	weak var delegate : NetworkOperationDelegate? = nil
	
	init(delegate : NetworkOperationDelegate? = nil) {
		self.delegate = delegate
	}
	
	func begin(input : Input) {
		self.delegate?.didMakeProgress(0)
		
		let request = NSURLRequest(URL: input)
		NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) { response, data, error in
			self.delegate?.didMakeProgress(100)
			if let data = data {
				self.output.value = data
			}
		}
	}
}

class JSONParseOperation : Operation {
	typealias Input = NSData
	typealias Output = AnyObject
	
	var input : Promise<Input>? {
		didSet {
			if let input = input?.getValue() {
				begin(input)
			}
		}
	}
	
	var output = Promise<Output>()
	
	func begin(input : Input) {
		let json : AnyObject = NSJSONSerialization.JSONObjectWithData(input, options: nil, error: nil)!
		output.value = json
	}
}

let url = NSURL(string: "http://ufd.dk")

let operation = Promise(value: url) >>> NetworkOperation(delegate: nil) >>> JSONParseOperation()

operation.output.waitForValue { value in
	println("json: \(value)")
}

let netop = Promise(value: url) >>> NetworkOperation()