Run a method after n seconds
The whole family performSelector is really interesting and can be useful in a multitude of cases. Its application simplest and most common is the following:
1 2 3 4 5 | @selector ( myMethod ) withObject : nil afterDelay : 3 ] ; [Self performSelector: @ selector (myMethod) withObject: nil afterDelay: 3]; / / void ) myMethod { - (Void) myMethod { "Hello World!" ) ; NSLog (@ "Hello World!"); } |
However, consider that the "timer" is not accurate. This procedure, therefore, should be used when it is not prompted for a "significant" temporal precision.
Retrieve the version of the application
1 2 |
YES, TRUE or false?
e TRUE sono in pratica la stessa edentica cosa: Going to comb through the Kernel Apple iPhone you can realize that YES , true and TRUE edentica are basically the same thing:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | / / Definition of the YES # Define YES (BOOL) 1 # Define NO (BOOL) 0 / / Definition of true # Define true 1 # Define false 0 / / Definition of TRUE # If! Defined (TRUE) # Define TRUE 1 # Endif # If! Defined (FALSE) # Define FALSE 0 # Endif |
At least for now ...
Chatter
1 2 3 | # Import <AudioToolbox/AudioToolbox.h> / / ; AudioServicesPlaySystemSound (kSystemSoundID_Vibrate); |
Pointer CGImageRef from a UIImage
1 2 3 4 | [ UIImage imageNamed : @ "LittleHeart.png" ] ; UIImage * heart = [UIImage imageNamed: @ "LittleHeart.png"]; heart CGImage ] ; CGImageRef image = [heart CGImage]; / / The image can now be "rasterized" on a CGContextRef CGRect ) { 0 , 0 , 100 , 100 } , image ) ; CGContextDrawImage (c, (CGRect) {0, 0, 100, 100}, image); |
Animations
1 2 3 4 5 | nil context : NULL ] ; [UIView beginAnimations: nil context: NULL]; 1.5 ] ; [UIView setAnimationDuration: 1.5]; UIViewAnimationCurveEaseInOut ] ; [UIView setAnimationCurve: UIViewAnimationCurveEaseInOut]; / / ... ; [UIView commitAnimations]; |
NSLog
1 2 3 | "NSString object %@ " , myString ) ; NSLog (@ "NSString object% @", myString); "Float: %f " , myFloat ) ; NSLog (@ "float:% f", myFloat); "Integer: %i " , myInt ) ; NSLog (@ "Integer:% i", myInt); |
Converter RGB to UIColor
1 | # Define RGBA (r, g, b, a) [UIColor colorWithRed: r/255.0 green: blue g/255.0: b/255.0 alpha: a] |
Passing parameters to a NSTimer
Taking advantage of the parameter userInfo you can send a pointer to an object to the method invoked by our timer.
1 2 3 4 5 6 7 8 9 10 11 12 13 | scheduledTimerWithTimeInterval : 1 target : self selector : @selector ( timerMethod ) userInfo : objectPointer repeats : YES ] ; [ NSTimer scheduledTimerWithTimeInterval: 1 target: self selector: @ selector (timerMethod) userInfo: objectPointer repeats: YES]; / / ... void ) timerMethod : ( NSTimer * ) timer { - (Void) timerMethod: ( NSTimer *) timer { / / Retrieve the pointer to my object timer userInfo ] ; objectPointer = [timer userInfo]; / / Or myMethod ] ; [[Timer userInfo] myMethod]; [ [ timer userInfo ] myProperty ] ; int a = [[timer userInfo] myProperty]; / / Which is the same [ objectPointer myProperty ] ; int a = [objectPointer myProperty]; } |
Execution time
Here's a simple way to calculate short time needed to check the speed of execution of the code:
1 2 3 4 | ; CFAbsoluteTime initialTime CFAbsoluteTimeGetCurrent = (); / / ... code ; CFAbsoluteTime finalTime CFAbsoluteTimeGetCurrent = (); "Tempo trascorso %f" , finalTime - initialTime ) ; NSLog (@ "Elapsed time% f", finalTime - initialTime); |
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