View source for Swift code snippets

=Swift Code snippts=
Back To [[IOS_Swift]]
==[[Swift: Use NSUserDefaults to Store Persistence Data]]==

==[[Swift: Making Network Request Using NSURLConnection]]==

==[[Swift:Use AFNetworking setImageWithURL]]==

==[[Swift:Using UIRefreshControl]]==

==Example of fetching messages from Parse==
https://gist.github.com/sandofsky/7134b1ff90d235901254
==Auto Table Row Height==
<pre class="brush:swift">
//Auto table row height
 tableView.estimatedRowHeight = 92.0
 tableView.rowHeight = UITableViewAutomaticDimension
</pre>
==Navigation between storyboards==
===Navigate to Storyboard ID===
<pre class="brush:swift">
var vc = storyboard.instantiateViewControllerWithIdentifier("loginViewController") as UIViewController
window?.rootViewController = vc
</pre>
===Navigate Segue by Identifier===
First, drag a segue in storyboard and give it an identifier, then in the button action (or any action you like), do:
<pre class="brush:swift">
self.performSegueWithIdentifier("loginSegue", sender: self)
</pre>
===Get UIVewController from Navigation Controller===
Sometimes, you want to access the UIViewController from a navigation controller
<pre class="brush:swift">
var vc = storyboard?.instantiateViewControllerWithIdentifier("navigationID") as UINavigationController
var v = vc.viewControllers[0] as ViewController // [0] represents the first level UIViewController under NavigationController
</pre>
==Notification in Swift==
Listen notification in swift
<pre class="brush:swift">
func tweetSent(notification: NSNotification) {
    let newTweet:Dictionary<String, Tweet> = notification.userInfo as Dictionary<String, Tweet>
}
NSNotificationCenter.defaultCenter().addObserver(self, selector: "tweetSent:", name: "newTweetNotification", object: nil)
</pre>
Send/Post notification in swift
<pre class="brush:swift">
var userInfo: Dictionary<String, Tweet> = ["tweet": newTweet]
NSNotificationCenter.defaultCenter().postNotificationName("newTweetNotification", object: nil, userInfo: userInfo)
</pre>
Remove notification observer
<pre class="brush:swift">
deinit {
    NSNotificationCenter.defaultCenter().removeObserver(self)
}
</pre>
==Get Raw Histogram from CGImage in swift==
Credit to http://stackoverflow.com/questions/27237297/how-to-get-meaningful-ciareahistogram-output

<pre class="brush:swift">
//dataImage is a CGImage
var imageData: CFDataRef = CGDataProviderCopyData(CGImageGetDataProvider(dataImage))
var dataInput: UnsafePointer<UInt8> = CFDataGetBytePtr(imageData)
//In swift, I have to do 2 steps. Not sure if there is any better way
var dataInputMutable = UnsafeMutablePointer<Void>(dataInput)
var height: vImagePixelCount = CGImageGetHeight(dataImage)
var width: vImagePixelCount = CGImageGetWidth(dataImage)
//Build a vImage_Buffer for next step
var vImageBuffer = vImage_Buffer(data: dataInputMutable, height: height, width: width, rowBytes: CGImageGetBytesPerRow(dataImage))
//Build the output array.
//To init a multi-dimensional UnsafeMutablePointer array. I have to do 3 steps
//First alloc sub arrays
var r = UnsafeMutablePointer<vImagePixelCount>.alloc(256)
var g = UnsafeMutablePointer<vImagePixelCount>.alloc(256)
var b = UnsafeMutablePointer<vImagePixelCount>.alloc(256)
var a = UnsafeMutablePointer<vImagePixelCount>.alloc(256)
//Then alloc main array
var histogram = UnsafeMutablePointer<UnsafeMutablePointer<vImagePixelCount>>.alloc(4)
//Set the pointer of sub arrays
histogram[0] = r
histogram[1] = g
histogram[2] = b
histogram[3] = a
//Finally, do the histogram calculation
var error:vImage_Error = vImageHistogramCalculation_ARGB8888(&vImageBuffer, histogram, 0);
        
if (error == kvImageNoError) {
    for var j = 0; j < 256; j++ {
        let currentVal = histogram[0][j] + histogram[1][j] + histogram[2][j] //I am making a grey histogram
        if currentVal > 0 {
            println("j=\(j),\(currentVal)")
        }
    }
    //delloc. MUST do this manually to prevent memory leak
    r.dealloc(256)
    g.dealloc(256)
    b.dealloc(256)
    a.dealloc(256)
    histogram.dealloc(4)
} else {
    println("Histogram vImage error: \(error)")
}
</pre>
==Xcode Swift Create Custom UIColor==
<pre class="brush:swift">let swiftColor = UIColor(red: 1, green: 165/255, blue: 0, alpha: 1)</pre>

==UIGraphics Drawing on UIView==
===Swift: Tutorial Drawing Graphic===
See http://www.techotopia.com/index.php/An_iOS_8_Swift_Graphics_Tutorial_using_Core_Graphics_and_Core_Image

===Swift: How to make UIGraphics context background transparent===
If you want to set a transparent background of the content you are drawing.
<pre class="brush:swift">
// UIGraphics draw transparent background context
@IBOutlet weak var histogramView: HistogramView!
override func viewWillAppear(animated: Bool) {
    histogramView.opaque = false 
    histogramView.backgroundColor = UIColor.clearColor()
}
class HistogramView: UIView {
    override func drawRect(rect: CGRect) {
        // draw content
        let context = UIGraphicsGetCurrentContext()
        CGContextClearRect(context, rect)
    }
}
</pre>

==Swift: Scale down CGImage==
<pre class="brush:swift">
func scaleDownCGImage(image: CGImage, scale: Float) -> CGImage!{
    var scaleDiv = UInt(1.0 / scale)
    let width = CGImageGetWidth(image) / scaleDiv
    let height = CGImageGetHeight(image) / scaleDiv
    let bitsPerComponent = CGImageGetBitsPerComponent(image)
    let bytesPerRow = CGImageGetBytesPerRow(image)
    let colorSpace = CGImageGetColorSpace(image)
    let bitmapInfo = CGImageGetBitmapInfo(image)
    let context = CGBitmapContextCreate(nil, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo)
    CGContextSetInterpolationQuality(context, kCGInterpolationMedium)
    let imgSize = CGSize(width: Int(width), height: Int(height))
    CGContextDrawImage(context, CGRect(origin: CGPointZero, size: imgSize), image)
    return CGBitmapContextCreateImage(context)
}
</pre>


==Swift: Convert between CGImage, CIImage and UIImage==
===Swift: Convert CIImage to CGImage===
<pre class="brush:swift">
func convertCIImageToCGImage(inputImage: CIImage) -> CGImage! {
    let context = CIContext(options: nil)
    if context != nil {
        return context.createCGImage(inputImage, fromRect: inputImage.extent())
    }
    return nil
}
</pre>
===Swift: Convert CGImage to CIImage===
<pre class="brush:swift">
func convertCGImageToCIImage(inputImage: CGImage) -> CIImage! {
   var ciImage = CIImage(CGImage: inputImage)
    return ciImage
}
</pre>
===Swift: Convert CGImage or CIImage to UIImage===
<pre class="brush:swift">
UIImage(CGImage: cgImage)
UIImage(CIImage: ciImage)
</pre>
===Swift: Convert UIImage to CIImage===
<pre class="brush:swift">
//uiImage: UIImage
//Convert to CIImage
var ciImage = CIImage(image: uiImage)
</pre>
===Swift: Convert UIImage to CGImage===
To convert to CGImage, it requires 2 steps: 

First convert to CIImage [[#Swift: Convert UIImage to CIImage]].

Then convert to CGImage [[#Swift:_Convert_CIImage_to_CGImage]]

==Swift Detect Volumn Button Press==
Credit to http://stackoverflow.com/questions/28471481/swift-detect-volume-button-press

Detect volume button press, also hide volume HUD

<pre class="brush:swift">
import MediaPlayer //Only for hidding  Volume view
func listenVolumeButton(){

    let audioSession = AVAudioSession.sharedInstance()
    audioSession.setActive(true, error: nil)
    audioSession.addObserver(self, forKeyPath: "outputVolume", options: NSKeyValueObservingOptions.New, context: nil)
    //If you want to hide Volume HUD view
    var volumeView: MPVolumeView = MPVolumeView(frame: CGRectZero)
    view.addSubview(volumeView)
}

override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject,
    change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
    if keyPath == "outputVolume"{
        print("got in here")
    }
}

</pre>