PrimeCheck Swift App Code. Has text field as first responder and dismiss on tap.

primechecker_viewcontroller.swift

//
//  ViewController.swift
//  PrimeChecker
//
//  2/7/16.
//  CC BY carlynorama.
//

import UIKit

class ViewController: UIViewController {
    

    @IBOutlet weak var numberTextField: UITextField!
    @IBOutlet weak var resultMessage: UILabel!
    
    @IBAction func submitButton(sender: UIButton) {
        if let numberToCheck = Int(numberTextField.text!) {
            if isPrime(numberToCheck) {
                resultMessage.text = "PRRRIIIIME!"
            } else {
                resultMessage.text = "not prime"
            }
        } else {
            resultMessage.text = "Please enter a postive integer."
        }

    }
    
    
    
    func isEven(n: Int) -> Bool { return n % 2 == 0 }
    func isDivisableByThree(n: Int) -> Bool { return n % 3 == 0 }
    func isDivisableByFive(n: Int) -> Bool { return n % 5 == 0 }
    func sixKplus1(n: Int) -> Bool { return (n-1) % 6 == 0 }
    func sixKminus1(n: Int) -> Bool { return (n+1) % 6 == 0 }
    
    func possibleFactors(n: Int) -> Array<Int> {
        var intArray: [Int] = Array(0...Int(sqrt(Double(n))))
        for (i, _) in intArray.enumerate().reverse(){
            switch intArray[i]{
            case Int.min..<3:
                intArray.removeAtIndex(i)
            case let x where isEven(x):
                intArray.removeAtIndex(i)
            case let x where isDivisableByThree(x):
                intArray.removeAtIndex(i)
            case let x where isDivisableByFive(x):
                intArray.removeAtIndex(i)
            case let x where sixKminus1(x):
                continue
            case let x where sixKplus1(x):
                continue
            default:
                intArray.removeAtIndex(i)
            }
        }
        print(intArray)
        return intArray
    }
    
    func hasFactors(n: Int) -> Bool {
        let checkThese = possibleFactors(n)
        for (i, _) in checkThese.enumerate() {
            if n % checkThese[i] != 0 {
                continue
            } else {
                return true
            }
        }
        return false
    }
    
    
    func isPrime(checkMe: Int) ->Bool {
        
        switch checkMe {
        case Int.min..<1:
            print("1 or smaller")
            return false
        case 2,3:
            print("2 or 3")
            return true
        case let x where isEven(x):
            print("divisible by 2")
            return false
        case let x where isDivisableByThree(x):
            print("divisible by 3")
            return false
        case let x where isDivisableByFive(x):
            print("divisible by 5")
            return false
        case let x where hasFactors(x):
            print("long factors check")
            return false
        default:
            print("defaulted out")
            return true
        }
        
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        numberTextField.becomeFirstResponder()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    
    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?){
        view.endEditing(true)
        super.touchesBegan(touches, withEvent: event)
    }
    
}