Add and align UIBarButtonItems to a UIToolbar

//This will add the addButton on the rightmost corner of the UIToolbar (toolbar)

UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addTasks:)];
	UIBarButtonItem *BtnSpace = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:self action:nil];
	[toolbar setItems:[NSArray arrayWithObjects:BtnSpace,addButton, nil] animated:YES];

Adding and Removing Subviews

//The first example is adding a subview to your MainWindow nib so that it loads a nib from another view controller.
//The following code goes in the AppDelegate.m under the following method

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    // Override point for customization after application launch
	[window addSubview:switchViewController.view]; //replace switchViewController with your own viewController
    [window makeKeyAndVisible];
	
	return YES;
}

//The second example shows how to add subviews to a viewController
//This would go in the view controller you are adding subviews to.
- (void)viewDidLoad {
    [super viewDidLoad];
	
	//In this case, BlueViewController is a viewController that is being called in this viewController (switchViewController)
	BlueViewController *blueController = [[BlueViewController alloc] initWithNibName:@"BlueViewController" bundle:nil];
	self.blueViewController = blueController;
	[self.view insertSubview:blueController.view atIndex:0]; //index 0 determines zindex.
	[blueController release];
}


//This example shows how to remove views (like the one above)
[yellowViewController.view removeFromSuperview];

//You can also check to see if the view of a given viewController is present using the following:
if (self.blueViewController.view.superview == nil) {
	...	
}

Alert View

	UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Test" message:@"clicked" delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];
	[alert show];
	[alert release];

Creating a Flip Animation between 2 ViewControllers

-(IBAction)switchViews:(id)sender {

	//Create the second view (the one that is not showing)
	if (self.yellowViewController == nil) {
	
		//Supply your own nib name here ofcourse...
		YellowViewController *yellowController = [[YellowViewController alloc] initWithNibName:@"YellowViewController" bundle:nil];
		self.yellowViewController = yellowController;
		[yellowController release];
	}
	
	[UIView beginAnimations:@"View Flip" context:nil];
	[UIView setAnimationDuration:1.25];
	[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
	
	
	//The if/else below looks at which view is showing, so that it knows what to hide and what to show
	
	//The blueviewcontroller is nil, which means the yellow one must be showing..
	if (self.blueViewController.view.superview == nil) {
	
		/*
		* Instead of FlipFromRight, we could have used:
		* UIViewAnimationTransitionFlipFromRight
		* UIViewAnimationTransitionFlipFromLeft
		* UIViewAnimationTransitionCurlUp
		* UIViewAnimationTransitionCurlDown
		*/
		
		//Always have cache:YES unless you want the view look to change during the animation (like it does in Classics page flip)
		
		[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES];
		[blueViewController viewWillAppear:YES];
		[yellowViewController viewWillDisappear:YES];
		
		[yellowViewController.view removeFromSuperview];
		[self.view insertSubview:blueViewController.view atIndex:0];
		
		[blueViewController viewDidAppear:YES];
		[yellowViewController viewDidDisappear:YES];
	}
	
	//The blue one is showing
	else {
		[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:self.view cache:YES];
		
		[yellowViewController viewWillAppear:YES];
		[blueViewController viewWillDisappear:YES];
		
		
		[blueViewController.view removeFromSuperview];
		[self.view insertSubview:yellowViewController.view atIndex:0];
		
		[yellowViewController viewDidAppear:YES];
		[blueViewController viewDidDisappear:YES];
	}
	
	
	//Need this!!
	[UIView commitAnimations];

}

Creating a PopOverView with a Navigation Bar

// in view.didload
//addTaskViewController is the view shown inside the popover
//The popover is wrapped in a UINavigationController

	//create add popover with a navigation bar attached
	addTaskViewController = [[AddTaskViewController alloc] initWithNibName:@"AddTaskViewController" bundle:nil];
	UINavigationController *addTaskNavController = [[UINavigationController alloc] initWithRootViewController:addTaskViewController];
	UIPopoverController *addTaskPopOver = [[UIPopoverController alloc] initWithContentViewController:addTaskNavController];
	self.addTaskPopOverController = addTaskPopOver;
	addTaskPopOverController.delegate = self;
	[addTaskPopOver release];
	
	
//Create a button to show the popover from (in view.didload)
	//create add ('+') button to the righthand side of the toolbar
	UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addTasksButtonPressed:)];
	UIBarButtonItem *BtnSpace = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:self action:nil];
	[toolbar setItems:[NSArray arrayWithObjects:BtnSpace,addButton, nil] animated:YES];
	[addButton release];
	
	
	//Implement addTasksButtonPressed:(id)sender;
	- (void) addTasksButtonPressed:(id)sender {
	[self.addTaskPopOverController setPopoverContentSize:CGSizeMake(400, 250)];
	[addTaskPopOverController presentPopoverFromBarButtonItem:sender permittedArrowDirections:UIPopoverArrowDirectionUp animated:YES];
}

Creating a UIButton and its Target Method

	UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addTask:)];
	
	
- (void) addTasks:(id)sender {
//...
}

Creating NSDate Object from components

// Get the Gregorian calendar
NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

// Get the date
NSDate* now = [NSDate date];

// Get the hours, minutes, seconds
NSDateComponents* nowHour = [cal components:NSHourCalendarUnit fromDate:now];
NSDateComponents* nowMinute = [cal components:NSMinuteCalendarUnit fromDate:now];
NSDateComponents* nowSecond = [cal components:NSSecondCalendarUnit fromDate:now];

Getting date components from NSDate

// just some date
NSDate *fooDate = [NSDate date];
// setting units we would like to use in future
unsigned units = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit | NSWeekdayCalendarUnit;
// creating NSCalendar object
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
// extracting components from date
NSDateComponents *components = [calendar components:units fromDate:fooDate];

// getting our fooDate components. On at the time. Oh, and they're integers!
[components year];
[components month];
[components day];
[components weekday];

Presenting a View Controller's view Modally for iPad

	//This is your modal view controller
	addProjectViewController = [[AddProjectViewController alloc] initWithNibName:@"AddProjectViewController" bundle:nil];
	UINavigationController *modalNavigationController = [[UINavigationController alloc] initWithRootViewController:addProjectViewController];
	
	//Set up Modal styles
	modalNavigationController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
	modalNavigationController.modalPresentationStyle = UIModalPresentationFormSheet;
	
	//self refers to the view controller showing the modal view controller
	[self presentModalViewController:modalNavigationController animated:YES];
	
	//release controllers from memory
	[addProjectViewController release];
	[modalNavigationController release];
	
	
	//To Dismiss, go to the Modal View Controller and call:
	[self dismissModalViewControllerAnimated:YES];