olbrichj

func attempt<T>(maximumRetryCount: Int = 3, delayBeforeRetry: DispatchTimeInterval = .seconds(2), _ body: @escaping () -> Promise<T>) -> Promise<T> {
    var attempts = 0
    func attempt() -> Promise<T> {
        attempts += 1
        return body().recover { error -> Promise<T> in
            guard attempts < maximumRetryCount else { throw error }
            return after(delayBeforeRetry).then(on: nil, attempt)
        }
    }
    return attempt()

olbrichj

func executeOnMain() {
  if !Thread.isMainThread {
    DispatchQueue.main.async(execute: {() -> Void in
      executeOnMain()
    })
    return
  }
  
  // do something
}

olbrichj

precedencegroup OperationChaining {
    associativity: left
}
infix operator ==> : OperationChaining

@discardableResult
func ==><T: Operation>(lhs: T, rhs: T) -> T {
    rhs.addDependency(lhs)
    return rhs
}

olbrichj

class Account: NSObject {
    var balance: Double
    var id: Int
    
    override init(id: Int, balance: Double) {
        self.id = id
        self.balance = balance
    }
    
    func withdraw(amount: Double) {

olbrichj

//Processor #1:
while f == 0 {
  OSMemoryBarrier()
  print x
}

//Processor #2:
x = 42
OSMemoryBarrier()
f = 1

olbrichj

//Processor #1:
while f == 0 {
  print x
}

//Processor #2:
x = 42
f = 1

olbrichj

var x = 100

func calculate() {
    var y = 0
    for i in 1...1000 {
        y += i
    }
    
    x = y
}

olbrichj

var title : [String] = []

func write(_ text: String) {
    let words = text.split(separator: " ")
    DispatchQueue.main.async {
        for word in words {
            title.append(String(word))
            print(word)
        }
    }

olbrichj

var title : [String] = []
var lock = NSLock()

func write(_ text: String) {
    let words = text.split(separator: " ")
    lock.lock()
    for word in words {
        title.append(String(word))
        print(word)
    }

olbrichj

func write(_ text: String) {
    let words = text.split(separator: " ")
    for word in words {
        title.append(String(word))
    }
}

write("Concurrency with Swift:") // Thread 1
write("What could possibly go wrong?") // Thread 2