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for view in self.view.subviews as! [UIView] { if let textField = view as? UITextField { if textField.text == "" { // show error return } } }See "Downcasting" in the Swift book.Update for Swift 2: As of Swift 2/Xcode 7 this can be simplified.Due to the Objective-C "lightweight generics", self.view.subviews is already declared as [UIView] in Swift, therefore the cast is not necessary anymore.Enume..

For-In LoopsYou use the for-in loop to iterate over a sequence, such as ranges of numbers, items in an array, or characters in a string.This example prints the first few entries in the five-times table:for index in 1...5 { print("\(index) times 5 is \(index * 5)")}// 1 times 5 is 5// 2 times 5 is 10// 3 times 5 is 15// 4 times 5 is 20// 5 times 5 is 25The sequence being iterated over is a range ..