Although UIView does not allow you round its corners, CALayer does, and every UIView is backed by a CALayer.

To access all of the functionality of CALayer, you will need to import QuartzCore into any of header/implementation files that you intend to use CALayer in.

#import <QuartzCore/QuartzCore.h>

CALayer has a lot of APIs available to it, but the property we are interested in is:

@property CGFloat cornerRadius

As the property suggests, this allows you to set the CALayer‘s corner radius in points:

UIView *view = [[UIView alloc] initWithFrame:frame];
view.layer.cornerRadius = 10.0;

CALayer also has properties allowing you to set its border, shadow etc, so all of these can save you a lot of code … and unwanted images.

The command is:

defaults write com.apple.Finder AppleShowAllFiles YES


The Finder needs to be restarted for this change to take effect. Luckily there is a Terminal command for this too:


killall Finder


Once you are done playing around with hidden files, you can stop showing them by replacing YES with NO in the original terminal command.


defaults write com.apple.Finder AppleShowAllFiles NO


It is as simple as that, but make sure your don’t break anything.

Although this information is very hard to find in the documentation, but is actually very easy to. The method you need to find is:

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- (BOOL)applicationShouldHandleReopen:(NSApplication *)theApplication hasVisibleWindows:(BOOL)flag;

This is an optional delegate method that your AppDelegate can choose to implement, and is called when the user presses your application’s dock icon. The bool flags indicates whether the application has any visible windows. To reopen your application’s main window, you need to have a pointer to it (In the example below assume that it is defined as NSWindow *window; in the header file). If you do have a pointer to then you simple need to implement the code below.

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- (BOOL)applicationShouldHandleReopen:(NSApplication *)theApplication hasVisibleWindows:(BOOL)flag{
 
	if(flag==NO){
		[window makeKeyAndOrderFront:self];	
	}
	return YES;	
}

It is as simple as that.

To change the name of an iPhone application is very easy. Simply open the Xcode project, and then scroll down to the “Targets” section, which the the “Groups & Files” part of Xcode. Select the application’s target and “Get info” on it using cmd-i or ctrl clicking it, and select “Get Info” from the menu.

In the build section of the get info window, you need to change the “Product Name” value to whatever you want your application to be called. When you change this value make sure that the configuration pop up menu (at the top of the window) is set to “All Configurations”, so it takes effect in all of your builds.

For the change of name to take effect, simply clean your targets and rebuild your application.


AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);


Categories are normally used for 2 things.

• Extending a class (using methods, not variables !!!)
• Logically separating a class into different functional areas

So lets look at something that is extremely popular at the moment ….. Twitter, and in paticular the 140 charachter limit.

Apple (for obvious reasons) don’t include Twitter related method calls on there string class NSString.

At the moment you would have to write everywhere in you code, something the resembles the following

NSString *twitterString=@"Objective-C rocks, I never want to look at Java again";
 
if([[twitterString] length]< 141)
{
//Post to twitter
}

Now this is good, but what if twitter changed their character limit, you would have to go an edit your code everywhere, where you used this check.
So we are going add a method to the NSString class:

 
- (BOOL)isUnderTwitterCharachterLimit;

This will make are code look like this

NSString *twitterString=@"Objective-C rocks, I never want to look at Java again";
 
if([twitterString isUnderTwitterCharachterLimit])
{
//Post to twitter
}

You now need an interface and implementation file, Im going to call them NSStringTwitterCategory.h and NSStringTwitterCategory.m

The interface file (NSStringTwitterCategory.h) is extremely small:

 
#import <Foundation/Foundation.h>
 
@interface NSString (Twitter)
 
-(BOOL)isUnderTwitterCharachterLimit;
@end

Instead of defining a new class in the format:


@interface NewClass: SuperClass{

}

You extend an existing class using the format:


@interface ClassYourExtending (CategoryName)


You can call the category whatever you want, but obviously you want to make it clear.

You then declare the methods like you always do.

The implementation file (NSStringTwitterCategory.m) is also not very complex:

@end


Again you extend the class in the same way as you did in the header file:


@implementation NSString (Twitter)


And you simple define the method as you normally would, nothing strange or fancy. If you want to use this category you just need to import the header file where you want to use it.

This is obviously a very simple example, but I hope it shows you how to use categories in Objective-C.

NSRange gives the starting location and the length of a given value, and is often used with arrays and strings. On this occasion we will use it to find the range of a substring within another string. If the range has a location, it contains the given substring. The following code does just that.

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NSRange textRange;
textRange =[string rangeOfString:substring];
 
if(textRange.location != NSNotFound)
{
 
//Does contain the substring
}

Making this a case insensitive compare is also very trivial, and can be done by lowercasing both strings

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NSRange textRange;
textRange =[[string lowercaseString] rangeOfString:[substring lowercaseString]];
 
if(textRange.location != NSNotFound)
{
 
//Does contain the substring
 
}