Check device OS version

Alertnative 1 :
NSArray *vComp = [[UIDevice currentDevice].systemVersion componentsSeparatedByString:@"."];

           
if ([[vComp objectAtIndex:0] intValue] >= 7) {

      // OS 7 code here

}

Alertnative 2 :
NSString *reqSysVer = @"7.0";
NSString *currSysVer = [[UIDevice currentDevice] systemVersion];

    

if ([currSysVer compare:reqSysVer options:NSNumericSearch] != NSOrderedAscending) {

     // OS 7 code here

}

Custom ActivityIndicator

//Display an Activity Indicator

-(void) displayActivityIndicator {

    // Set position for activityIndicator

    [self setActivityIndicatorPosition];

    

    [waitView setImage:[UIImage imageNamed:@"WaitScreen.png"]];

    

    activityIndicator= [[UIActivityIndicatorView alloc]

                        initWithActivityIndicatorStyle: UIActivityIndicatorViewStyleWhiteLarge];

    

    [activityIndicator setFrame:CGRectMake(86,30,30,30)];

    [activityIndicator startAnimating];

    

    [waitView addSubview: activityIndicator];

    

    [self.view] addSubview:waitView];

    

    [activityIndicator startAnimating];

    

    //Ignore interaction for background activities

    [[UIApplication sharedApplication] beginIgnoringInteractionEvents];

}

#pragma mark -

#pragma mark setActivityIndicatorPosition

-(void) setActivityIndicatorPosition {

       

    CGRect screenSize = [[UIScreen mainScreen] bounds];      

    

     if( ([UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationPortrait) || ( [UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationPortraitUpsideDown)) {

        

        [waitView setFrame:CGRectMake(x,y,203,73)];

    }

    

    if(([UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationLandscapeLeft ) || ([UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationLandscapeRight)) {

                

         [waitView setFrame:CGRectMake(x1,y1,203,73)];

    }    

}

//Hide Activity Indicator

-(void) hideActivityIndicator {

    

    //Hide waitView

    [waitView setImage:[UIImage imageNamed:nil]];

    [activityIndicator stopAnimating];

    

    if ([[UIApplication sharedApplication] isIgnoringInteractionEvents]) {

        

        // Start interaction with application

        [[UIApplication sharedApplication] endIgnoringInteractionEvents];

    }

       

}

                                 

 

NSUserDefault usage

 //Set NSUserDefault

NSString *somePersistantValue = @"null";

    

[[NSUserDefaults standardUserDefaults] setObject:somePersistantValue forKey:@"keyName"];

[[NSUserDefaults standardUserDefaults] synchronize];

 //Get NSUserDefault

NSString *fetchPersistantValue = [[NSUserDefaults standardUserDefaults] objectForKey:@"keyName"]; 

Set notification for Orientation

//Set Notification on Orientation change

[[NSNotificationCenter defaultCenter] addObserver:self  selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification  object:nil];

//  Handle orientation change

- (void)orientationChanged:(NSNotification *)notification {

    ...

}

Using camera / gallery of device

 UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];

        

//camera selection

if(buttonIndex == 0){

if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]){

                

imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;

imagePicker.delegate = self;

                

[self presentViewController:imagePicker animated:YES completion:nil];                

}

else {

                

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert" message:NSLocalizedString(@"DeviceItem", @"") delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];

                

[alert show];

}

}       

else if(buttonIndex == 1) {   //gallery selection

            

imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

            

   imagePicker.delegate=self;

   [self presentViewController:imagePicker animated:YES completion:nil];

}

Execute code in background

// Fetch legend details task in background

                 dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);

                 dispatch_after(popTime, dispatch_get_main_queue(), ^(void){

                     

                     // Perform task here

                 });

Check device orientation

UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;

 if ((orientation == UIInterfaceOrientationLandscapeLeft) || (orientation == UIInterfaceOrientationLandscapeRight)) {

     //Landscape mode

}

 else if ((orientation == UIInterfaceOrientationPortrait) || (orientation == UIInterfaceOrientationPortraitUpsideDown)) {

     //Portrait mode

}