import UIKit
import AVFoundation

class ViewController: UIViewController{
    
    var btnSound: AVAudioPlayer!
    override func viewDidLoad() {
        super.viewDidLoad()
        let path = NSBundle.mainBundle().pathForResource("btn", ofType: "wav")
        let soundUrl = NSURL(fileURLWithPath: path!)
        
        do {
            try btnSound = AVAudioPlayer(contentsOfURL: soundUrl)
            btnSound.prepareToPlay()
        } catch {
            
        }
    }
    ...

    @IBOutlet weak var monsterImg: UIImageView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        var imgArray = [UIImage]()
        //init your image array, for example
        for var x = 1; x <= 4; x++ {
            let img = UIImage(named: "idle\(x).png")
            imgArray.append(img!)
        }
        
        monsterImg.animationImages = imgArray
        monsterImg.animationDuration = 0.8
        monsterImg.animationRepeatCount = 0
        monsterImg.startAnimating()
        
        //animationImages
        //An array of UIImage objects to use for an animation.
        
        //animationDuration
        //The amount of time it takes to go through one cycle of the images.
        //The time duration is measured in seconds. The default value of this property is equal to the number of images multiplied by 1/30th of a second. Thus, if you had 30 images, the value would be 1 second.
        
        //animationRepeatCount
        //Specifies the number of times to repeat the animation.
        //The default value is 0, which specifies to repeat the animation indefinitely.
    }

import Foundation
import UIKit

class DragImg: UIImageView {
    
    var originalPosition: CGPoint!
    
    //why override this?
    override init(frame: CGRect) {
        super.init(frame: frame)
    }
    
    //what's this?
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        originalPosition = self.center
    }
    
    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
        if let touch = touches.first {
            let position = touch.locationInView(self.superview)
            self.center = CGPointMake(position.x, position.y)
        }
    }
    
    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        self.center = originalPosition
    }
}

var timer: NSTimer!
timer = NSTimer.scheduledTimerWithTimeInterval(TIME_INCREMENT, target:self, selector: "FUNCTION", userInfo: nil, repeats: BOOL)

//somewhere
NSNotificationCenter.defaultCenter().postNotification(NSNotification(name: "NOTIFICATION_NAME", object: nil))

//somewhere else
NSNotificationCenter.defaultCenter().addObserver(self, selector: "FUNCTION", name: "NOTIFICATION_NAME", object: nil)

    override init(frame: CGRect) {
        super.init(frame: frame)
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

//somewhere
  performSegueWithIdentifier("IDENTIFIER", sender: A_SENDER)
  
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyOBject?) {
  if segue.identifier == "IDENTIFIER" {
    if let whatVC = segue.destinationViewController as ? SomeViewController {
      if let theString = sender as? String {
        whatVC.someStr = theString
      }
    }
  }
}

extension Double {
  var currency: String {
    return "$\(self)"
  }
}

NSAppTransportSecurity Dictionary
NSAllowsArbitraryLoads Boolean YES

let tap = UITapGestureRecognizer(target: self, action: "dismissKeyboard")
tap.cancelsTouchesInView = false
view.addGestureRecognizer(tap)

func dismissKeyboard()
{
    view.endEditing(true)
}

func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    return UITableViewAutomaticDimension
}

func tableView(tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
    return UITableViewAutomaticDimension
}

view.frame.CGRectMake(0 , 0, self.view.frame.width, self.view.frame.height * 0.7) 

let layout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
layout.minimumInteritemSpacing = 1
layout.minimumLineSpacing = 1

collectionView.collectionViewLayout = layout

override func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell,
    forRowAtIndexPath indexPath: NSIndexPath) {
    //Animation Code
}

drawImage(UIImage(named: "image")!, size: CGSizeMake(30, 30), renderColor: UIColor(red: 149.0/255, green: 149.0/255, blue: 149.0/255, alpha: 1))

let text = (stringName as NSString).stringByReplacingOccurrencesOfString("whatever", withString: "")

if Int(strToCheck) == nil {
  print("Not Int")
} else {
  print("Is Int")
}

String.localizedStringWithFormat(NSLocalizedString("Blahblahblah %d.", comment: "Some Comment"), intVar)

import UIKit

class ExampleAlertView: UIView {
    
    
    @IBOutlet weak var wechatPayButton: UIButton!
    @IBOutlet weak var alipayButton: UIButton!
    
    @IBOutlet weak var amountTextField: UITextField!
    
    @IBOutlet weak var infoLabel: UILabel!
    
    private var shadowBtn: UIButton!
    
    let ApplicationDelegate = (UIApplication.sharedApplication().delegate as! AppDelegate)
    private var showView: UIView {
        return ApplicationDelegate.window!
    }
    
    private var confirmClosure: (() -> ())?
    private var cancelClosure: (() -> ())?
    
    
    @objc private func shadowBtnClick() {
        
        UIView.animateWithDuration(0.15, animations: {
            self.shadowBtn.alpha = 0
            self.alpha = 0
        }) { (success) in
            self.shadowBtn.removeFromSuperview()
            self.removeFromSuperview()
        }
    }

    class