UnsafeMutablePointer to NSString

Converting UnsafeMutablePointer<UInt8> to NSString.

Today I was using a function that was bridging from a third party library in Objective-C.

The function has two parameters, first parameter has a type of UnsafeMutablePointer<UInt8>, second one the type is Int32, which is the length of the char array.  My goal is convert it to NSString for logging information.

UnsafeMutablePointer<UInt8> is an array of char(or bytes) in the library API.

In order to do this, use NSString function:

convenience init?(bytes bytes: a href=”” UnsafePointer <Void >,
length length: Int,
encoding encoding: UInt )


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IOS – Subclass from UILabel in Swift

This is an example from a book I read: iOS Core Animation: Advanced Techniques 

The example in the book was written in Objective-C, which I would convert it into Swift Language as my learning reference.   The goal of this example is to create a subclass of UIView, and overrides the layerClass class method to return different layer subclass at creation time.  UIView calls the class method layerClass during its initiation, and uses the class it returns to create its backing layer.

In this example, a UILabel subclass called LayerLabel that draws its text using a CATextLayer instead of using the slower method drawRect approach that UILabel uses.

Some notes I marked down when converting from objective-c to swift:


1. NSObject class method is removed in Swift.

In objective-C example:

+(Class) layerClass {
 return [CATextLayer class];

Instead, in Swift, we can simply return CATextLayer.self as class

override class func layerClass() -> AnyClass {
  return CATextLayer.self



2. UIView initiation method now is called init() in Swift rather than initWithFrame: in Objective-C


In objective-C:

-(id) initWithFrame: (CGRect) frame {
if (self = [super initWithFrame: frame]) {
     [self setup];
return self;

In Swift:

required init(coder aDecoder: NSCoder) {

override init(frame:CGRect) {



    override  func awakeFromNib() {



Here is the example rewritten in Swift:


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Preventing Your IOS app from sleeping mode

Sometime, apps may need to prevent the sleeping mode to enhance user experience.  For example, an app that play video would not go into sleep while the movie is playing.  In IOS, a simple task can be done to prevent the app run into a sleep mode.

Just remember to turn on the sleeping mode whenever the task finish.  (for example, when your app stop playing video, you should turn the sleeping mode on again.

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