Im trying to run my calculator - ios

Question

Im using swift code on Xcode 8. Can someone please help me out and figure out the error? It says the expression pattern of type 'string' cannot match values of type 'operation'. the error appeared at the switch operation and then the case that held × in it.
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var display: UILabel!
var userIsInTheMiddleOfTyping = false
#IBAction func Appenddigit(_ sender: UIButton) {
let digit = sender.currentTitle!
if userIsInTheMiddleOfTyping {
display.text = display.text! + digit
} else {
display.text = digit
userIsInTheMiddleOfTyping = true
}
}
#IBAction func operate(_ sender: UIButton) {
_ = sender.currentTitle!
if userIsInTheMiddleOfTyping{
enter()
}
switch Operation() {
case "×":
if operandStack.count >= 2 {
displayValue = operandStack.removeLast() * .operandStack.removeLast()
enter()
}
// case "÷":
// case "+":
// case "−":
default:
break
}
}
var operandStack: Array<Double> = []
#IBAction func enter() {
userIsInTheMiddleOfTyping = false
operandStack.append(displayValue)
print("operandStack = \(operandStack)")
}
var displayValue: Double {
get {
return NumberFormatter().number(from: display.text!)!.doubleValue
}
set {
display.text = "\(newValue)"
userIsInTheMiddleOfTyping = false
}
}
}

Answer 1

In Swift 3, Operation is the new name of the class NSOperation.
Your expression Operation() is creating an Operation object.
Whatever "Operation" is in your program, you need to rename it to something else. You should also explain what that code is supposed to be doing so we can help you fix it. The line
switch Operation()
Doesn't make sense to me.

Answer 2

Operation() is creating a new object of type Operation which cant be compared to "x"which is a string. What i think you want is to be calling a function called operation which would return a string.