@IBAction func cf_changeCase(_ sender: NSButton) {
	if (sender.tag == 1) {
		cv_label.stringValue = cv_label.stringValue.uppercased()
	}
	else {
		cv_label.stringValue = cv_label.stringValue.lowercased()
	}
}

• ? -- can be either a value or nil
• ! -- must have a value
• Examples
  var bar : Int? bar = 10 bar = nil var foo : Int = 5 //foo = nil // error //foo = bar // error bar = 4 //foo = bar // error foo = bar!
• Horrible Mess! - every version has its own rules
• as?, as! (?as, !as, ?as!, !as?, ...) -- what a mess!

• a ... b -- [a, b]
• a ..< n -- [a, b)
• String Interpolation -- \()
• An Example
  for index in 1...5 { println("\(index) times 5 is \(index * 5)") } *** Swift 3+ println ==> print

• no input, no return
  void foo () { System.out.println("Hello Java"); } func foo() { print("Hello Swift") } foo()
• input, no return
  void foo (int a, int b, int c) { System.out.println("sum = " + a+b+c); } func foo(a: Int, b: Int, c: Int) { print("sum = \(a+b+c)\n") } foo(a:1,b:2,c:3) *** foo(1,2,3) NOT allowed func foo(a: Int, b: Int, c: Int) -> Void { print("sum = \(a+b+c)\n") } is preferred
• no input, return
  int iR () { int iRand = (int) (Math.random() * 10) + 1; return iRand; } import Darwin // or Foundation func iR() -> UInt32 { let iRand : UInt32 = arc4random() % 10; return iRand; } iR() print (iR())
• input, return
  double sum (double a[]) { double s = 0.0; for (int i=0; i < a.length; a++) { s += a[i] } return s; } func sum(a: [Double]) -> Double { var s = 0.0 // var s : Double = 0.0 for i in 0 ..< a.count { s += a[i] } return s } sum(a:[1.0, 2.0]) print( sum(a:[1.0, 2.0]) )
• multiple return values
  let val : Double = 12.34 func foo(input : Double) -> (Int, Double) { let whole = Int(input) let frac = input - Double(whole) return (whole, frac) } foo(input:val).0 foo(input:val).1 print(foo(input:val))

• To define/call, two approaches -- by position, by name
• Java -- by position
• Swift -- by name
• Objective C -- by ??