iOS code bites;

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Hello iFellows; 
Hope all are enjoying your life;

Today, there are  some tips for new iDevelopers; These code chunks will help you out to do some really simple and many-time useable thing;

Bring coke and have some light track in iTune;

So here we go;


In Xcode, click Run > Console to see NSLog statements.

NSLog(@"log: %@ ", myString);
 NSLog(@"log: %f ", myFloat);
 NSLog(@"log: %i ", myInt);

Display Images

Display an image anywhere on the screen, without using UI Builder. You can use this for other types of views as well.

CGRect myImageRect = CGRectMake(0.0f, 0.0f, 320.0f, 109.0f);
UIImageView *myImage = [[UIImageView alloc] initWithFrame:myImageRect];
[myImage setImage:[UIImage imageNamed:@"myImage.png"]];
myImage.opaque = YES; // explicitly opaque for performance
[self.view addSubview:myImage];
[myImage release];

Application Frame

Use “bounds” instead of “applicationFrame” — the latter will introduce a 20 pixel empty status bar (unless you want that..)

Web view

A basic UIWebView.

CGRect webFrame = CGRectMake(0.0, 0.0, 320.0, 460.0);
 UIWebView *webView = [[UIWebView alloc] initWithFrame:webFrame];
 [webView setBackgroundColor:[UIColor whiteColor]];
 NSString *urlAddress = @"";
 NSURL *url = [NSURL URLWithString:urlAddress];
 NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
 [webView loadRequest:requestObj];
 [self addSubview:webView];
 [webView release];
Display the Network Activity Status Indicator

This is the rotating icon displayed on the iPhone status bar in the upper left to indicate there is background network activity taking place.

UIApplication* app = [UIApplication sharedApplication];
 app.networkActivityIndicatorVisible = YES; // to stop it, set this to NO

Animation with Series of images

Show a series of images in succession

NSArray *myImages = [NSArray arrayWithObjects: [UIImage imageNamed:@”myImage1.png”],
[UIImage imageNamed:@”myImage2.png”],
[UIImage imageNamed:@”myImage3.png”],
[UIImage imageNamed:@”myImage4.gif”],  nil];
UIImageView *myAnimatedView = [UIImageView alloc];
[myAnimatedView initWithFrame:[self bounds]];
myAnimatedView.animationImages = myImages;
myAnimatedView.animationDuration = 0.25; // seconds
myAnimatedView.animationRepeatCount = 0; // 0 = loops forever
[myAnimatedView startAnimating];
[self addSubview:myAnimatedView];
[myAnimatedView release];

Animation: Move an object

Show something moving across the screen. Note: this type of animation is “fire and forget” — you cannot obtain any information about the objects during animation (such as current position). If you need this information, you will want to animate manually using a Timer and adjusting the x&y coordinates as necessary.

CABasicAnimation *theAnimation;
theAnimation=[CABasicAnimation animationWithKeyPath:@”transform.translation.x”];
theAnimation.fromValue=[NSNumber numberWithFloat:0];
theAnimation.toValue=[NSNumber numberWithFloat:-60];
[view.layer addAnimation:theAnimation forKey:@”animateLayer”];

NSString and int

The following example displays an integer’s value as a text label:

currentScoreLabel.text = [NSString stringWithFormat:@”%d”, currentScore];

Draggable items

Here’s how to create a simple draggable image.
1. Create a new class that inherits from UIImageView

@interface myDraggableImage : UIImageView

2. In the implementation for this new class, add the 2 methods:

– (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
// Retrieve the touch point
CGPoint pt = [[touches anyObject] locationInView:self];
startLocation = pt;
[[self superview] bringSubviewToFront:self];

} – (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
// Move relative to the original touch point
CGPoint pt = [[touches anyObject] locationInView:self];
CGRect frame = [self frame];
frame.origin.x += pt.x – startLocation.x;
frame.origin.y += pt.y – startLocation.y;
[self setFrame:frame];

3. Now instantiate the new class as you would any other new image and add it to your view

dragger = [[myDraggableImage alloc] initWithFrame:myDragRect];
[dragger setImage:[UIImage imageNamed:@”myImage.png”]];
[dragger setUserInteractionEnabled:YES];

Vibration and Sound

Here is how to make the phone vibrate (Note: Vibration does not work in the Simulator, it only works on the device.)


Sound will work in the Simulator, however some sound (such as looped) has been reported as not working in Simulator or even altogether depending on the audio format. Note there are specific filetypes that must be used (.wav in this example).

SystemSoundID pmph;
id sndpath = [[NSBundle mainBundle]
pathForResource:@”mySound” ofType:@”wav” inDirectory:@”/”];
CFURLRef baseURL = (CFURLRef) [[NSURL alloc] initFileURLWithPath:sndpath];
AudioServicesCreateSystemSoundID (baseURL, &pmph);
[baseURL release];


1. Create the new thread:

[NSThread detachNewThreadSelector:@selector(myMethod)   toTarget:self       withObject:nil];

2. Create the method that is called by the new thread:

– (void)myMethod {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
*** code that should be run in the new thread goes here ***
[pool release];

What if you need to do something to the main thread from inside your new thread (for example, show a loading symbol)? UseperformSelectorOnMainThread.

[self performSelectorOnMainThread:@selector(myMethod) withObject:nil waitUntilDone:false];

Reading crash logs

For this, see my other post  How to symbolicate iPhone Crash Reports;

Access properties/methods in other classes

One way to do this is via the AppDelegate:

myAppDelegate *appDelegate   = (myAppDelegate *)[[UIApplication sharedApplication] delegate];
[[[appDelegate rootViewController] flipsideViewController] myMethod];


This timer will call myMethod every 1 second.

[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(myMethod) userInfo:nil repeats:YES];

What if you need to pass an object to myMethod? Use the “userInfo” property.
1. First create the Timer

[NSTimer scheduledTimerWithTimeInterval:1 target:self  selector:@selector(myMethod) userInfo:myObject repeats:YES];

2. Then pass the NSTimer object to your method:

-(void)myMethod:(NSTimer*)timer {
         [[timer userInfo] myObjectMethod];

To stop a timer, use “invalidate”:

[myTimer invalidate]; myTimer = nil; // ensures we never invalidate an already invalid Timer

Plist files

Application-specific plist files can be stored in the Resources folder of the app bundle. When the app first launches, it should check if there is an existing plist in the user’s Documents folder, and if not it should copy the plist from the app bundle.

// Look in Documents for an existing plist file
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
myPlistPath = [documentsDirectory stringByAppendingPathComponent:
[NSString stringWithFormat: @”%@.plist”, plistName] ];
[myPlistPath retain];  // If it’s not there, copy it from the bundle
NSFileManager *fileManger = [NSFileManager defaultManager];
if ( ![fileManger fileExistsAtPath:myPlistPath] ) {
NSString *pathToSettingsInBundle = [[NSBundle mainBundle] pathForResource:plistName ofType:@”plist”];

Now read the plist file from Documents

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectoryPath = [paths objectAtIndex:0];
NSString *path = [documentsDirectoryPath stringByAppendingPathComponent:@”myApp.plist”];
NSMutableDictionary *plist = [NSDictionary dictionaryWithContentsOfFile: path];

Now read and set key/values

myKey = (int)[[plist valueForKey:@”myKey”] intValue];
myKey2 = (bool)[[plist valueForKey:@”myKey2″] boolValue];
[plist setValue:myKey forKey:@”myKey”];
[plist writeToFile:path atomically:YES];

Thats all from today’s class;
Happy Development my fellow professionals;


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2 thoughts on “iOS code bites;

    wilddogs said:
    June 13, 2011 at 16:00

    I have an image in a webView, but it keeps bouncing up or down when swiped instead of changing to the next image (a gallery app)

    It works fine in iPhone, the image is firmly placed and responds to swipe gesture properly.

    The iPad version has the swipe gesture activated in the toolbar (not the webView) !

    What can I do? Help!

      Ans responded:
      June 13, 2011 at 16:07

      can you describe your problem in little more detail?
      What i have understood is an image in webview is not responding well to swap gesture, in iPad version;
      is that?

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