Blocks have two major benefits (although there are more):

• They can be used in conjunction with Grand Central Dispatch (GCD), as an alternative to threading.
• They can be used for callbacks, instead of NSNotifications, callback selectors, function pointers etc. This is usually done by providing a callback/completion block, and this is what we will be looking at here.

The most common method that you will use to animate views using blocks, is the following class method on UIView:

+ (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion;

This method allows you to set a time interval, along with an animations block and a completion block.

Lets say we have a UIView variable called redView.

redView = [[UIView alloc] initWithFrame:CGRectMake(0,0,320,320)];
redView.backgroundColor = [UIColor redColor];

We will then add redView as a subview of the view controller’s view

[self.view addSubview:redView];

A common situation you may find your self in, is when you finish animating a view (e.g. changing its alpha), you would then want to remove it from it’s superview, and then release it from memory.

So if you had (for example) a method called animate to trigger off the animation, you would need to add an “animation did stop selector” to the animation. In the following example I have called it cleanUp.

- (void)animate{
 
   [UIView beginAnimations:@"" context:NULL];
   [UIView setAnimationDuration:5.0];
   [UIView setAnimationDidStopSelector:@selector(cleanUp)];
   [redView setAlpha:0.0];
   [UIView commitAnimations];
 
}
 
- (void)cleanUp{
 
    [redView removeFromSuperview];
    //I do release and = nil on the same line as a coding convention
    //so I don't forget to "nil" the variable
    [redView release], redView = nil;	
}

Although this works well enough, it does mean that your code is split up into the animation code and the (completion) clean up code. If you end up doing this a lot, your code can end up becoming very fragmented and hard to follow.

Using blocks we can do the following:

- (void)animate{
 
[UIView animateWithDuration:5.0
 
                            animations:^{ 
	                          redView.alpha = 0.0; 
	                     }
 
                           completion:^(BOOL  completed){
	                          [redView removeFromSuperview];
                                  [redView release],redView = nil;
	                    }
 ];
 
 
}

This keeps things nice and simple, and it means that you can easily see what code will be executed when the animation completes.

All of the animations you wish to do are passed in using a block:

 
^{ 
redView.alpha = 0.0; 
}

This block takes no arguments, and it also does not have a return type (so it defaults to void).

Instead of calling the cleanUp selector, we can simply pass in a completion block:

 
^(BOOL  completed){
[redView removeFromSuperview];
[redView release],redView = nil;
}

This block takes one parameter, which is a bool signifying if the animation has completed when the block is executed. In this example we ignore the completed variable, and we assume that the animation has completed for simplicity reasons. In the body of the block we do same as we did in the cleanUp selector, we remove redView from its super view and then release it from memory.

In some situations you won’t need to use blocks for Core Animation, but when you do, you will find it cleans up your code no end.

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.

Each application has its own MPMusicPlayerController, but it also has access to the iPod’s MPMusicPlayerController, using the class method iPodMusicPlayer.

MPMusicPlayerController *iPodMusicPlayerController = [MPMusicPlayerController iPodMusicPlayer];

After you have got the iPod music player, you can then get the now playing item

MPMediaItem *nowPlayingItem = [iPodMusicPlayerController nowPlayingItem];

If the now playing item is nil, you know that the user is not playing a music track on their iPod.

Unlike many of the other APIs in iOS, you can’t access information such as the track name, via a simple string property. You have to use one of the following keys:

NSString *const MPMediaItemPropertyPersistentID;
NSString *const MPMediaItemPropertyMediaType; 
NSString *const MPMediaItemPropertyTitle;
NSString *const MPMediaItemPropertyAlbumTitle; 
NSString *const MPMediaItemPropertyArtist; 
NSString *const MPMediaItemPropertyAlbumArtist; 
NSString *const MPMediaItemPropertyGenre;
NSString *const MPMediaItemPropertyComposer; 
NSString *const MPMediaItemPropertyPlaybackDuration;
NSString *const MPMediaItemPropertyAlbumTrackNumber;
NSString *const MPMediaItemPropertyAlbumTrackCount;
NSString *const MPMediaItemPropertyDiscNumber;
NSString *const MPMediaItemPropertyDiscCount;
NSString *const MPMediaItemPropertyArtwork;
NSString *const MPMediaItemPropertyLyrics;
NSString *const MPMediaItemPropertyIsCompilation;  
NSString *const MPMediaItemPropertyReleaseDate;
NSString *const MPMediaItemPropertyBeatsPerMinute;
NSString *const MPMediaItemPropertyComments;
NSString *const MPMediaItemPropertyAssetURL;

And then query the Media Player Item, using the instance method valueForProperty:.

NSString *itemTitle = [nowPlayingItem valueForProperty:MPMediaItemPropertyTitle];

And thus you will end up with a code snippet like this:

MPMusicPlayerController *iPodMusicPlayerController = [MPMusicPlayerController iPodMusicPlayer];
 
MPMediaItem *nowPlayingItem = [iPodMusicPlayerController nowPlayingItem];	
 
if(nowPlayingItem)
{
    NSString *itemTitle = [nowPlayingItem valueForProperty:MPMediaItemPropertyTitle];
    NSLog(@"User is playing the following song: %@",itemTitle);
}else {
    NSLog(@"User is not playing a song");
}

As always this is just a small code snippet to get you started. There are situations for instance, where the user can have a now playing item that has no title (strange I know). So as always you will have to handle these edge cases appropriately.

MKMapView allows you to display a Map on your iPhone’s screen. MKMapView is just a subclass of UIView so you can treat it like one. You can ether use it as a subview (such as on a profile page), or make it go full screen (using it with its own view controller) such as when you are viewing a map to get directions.

So like UIView, to create a MKMapView you need to initialise one with a frame:

MKMapView *mapView = [[MKMapView alloc] initWithFrame:CGRectMake(0,0,320,480)];

Unlike UIView, you will also want to become the delegate of MKMapView.

mapView.delegate = self;

The delegate methods for MKMapView include ones that inform you about when the map starts and finishes to load, in addition to if it fails to load at all. (These delegate methods are very similar to UIWebView if you have used that).

- (void)mapViewWillStartLoadingMap:(MKMapView *)mapView;
- (void)mapViewDidFinishLoadingMap:(MKMapView *)mapView;
- (void)mapViewDidFailLoadingMap:(MKMapView *)mapView withError:(NSError *)error;

In addition to the loading of the Map, the delegate also provides call backs for when the map’s region changes, it also provides callbacks regarding annotation information (more on that later).

- (void)mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated;
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated;

After you have created a MKMapView, you will want to show a specific region on the map. The method to do this is:

- (void)setRegion:(MKCoordinateRegion)region animated:(BOOL)animated;

This introduces a new MapKit data type MKCoordinateRegion. This is the centre point (that you want to show) expressed as a co-ordinate, and then the distance (span) around this co-ordinate that you want to be shown. In essence the span is the zoom level. The bigger the span, the bigger the area that is displayed on the map.

To make a new region you will need to use:

MKCoordinateRegionMake(CLLocationCoordinate2D centerCoordinate, MKCoordinateSpan span);

And thus you will probably have some code that looks like this:

CLLocationCoordinate2D coordinate;
coordinate.latitude = -122.03;
coordinate.longitude = 37.33;
 
MKCoordinateSpan  span = MKCoordinateSpanMake(0.003, 0.003);
 
[mapView setRegion:MKCoordinateRegionMake(coordinate, MKCoordinateSpanMake(0.003, 0.003)) animated:YES];

After you have focused in on a specific region of the map, you will more than likely want to annotate a given point. To do this you need to create an object that conforms to the (informal) MKAnnotation protocol, and in particular implements the CLLocationCoordinate2D coordinate property.

e.g.

@interface MCSMMapAnnotation : NSObject {
 
}
 
@property (nonatomic) CLLocationCoordinate2D coordinate;
 
@end

Then you just need to create an instance of this model object, and then add it to the map as an annotation:

MCSMMapAnnotation *annotation = [[MCSMMapAnnotation alloc] init];
 
CLLocationCoordinate2D annotationCoordinate;
coordinate.latitude = -122.03;
coordinate.longitude = 37.33;
annotation.coordinate = annotationCoordinate;
[self.mapView addAnnotation:annotation];

And that is it, nice and simple.

One more thing …

Before I mentioned that there are delegate methods regarding the annotations on the Map View. One that is particular useful is:

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)annotationViews;

Why is it useful ? Well if you didn’t notice, doing the above means that the annotation(s) just appear on the screen and they do not drop on. So in this delegate method, you can move the annotations off screen and then put them back to where MapKit said they should be.

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)annotationViews{
 
//The final (correct) position of the annotation
CGRect finalFrame;
 
//The position we will drop the annotation from
CGRect offScreenFrame;		
 
 
for(UIView *annotationView in annotationViews) {
 
//MapKit has worked out the annotations final position so store it
finalFrame = annotationView.frame;
 
//We just want to move the annotation, so it is just above the top of the visible screen
 
offScreenFrame = CGRectMake(finalFrame.origin.x,(finalFrame.size.height *-1) , finalFrame.size.width, finalFrame.size.height);
 
//Set and therefore move the annotation to the off screen position
annotationView.frame = offScreenFrame;
 
//Set up an animation block to animate the drop
[UIView beginAnimations:@"AnimateAnnotation" context:NULL];
[UIView setAnimationDuration:1.0];
 
//Set the final frame, to be the frame that map kit originally calculated
annotationView.frame = finalFrame;
[UIView commitAnimations];
}
 
 
}

This is just a brief overview of what you can do with MapKit. The most obvious thing you can do, is to add more than one annotation to the map, and the above animation trick is designed to work with this. One feature you may want to do if your application heavily relies upon maps, is to create your own custom pins (that don’t even need to look like pins), to point out specific points on the map.

When I first thought about this problem, I was thinking along the lines of build a custom log function lets say MagicLog() and this calls a function that saves the string to a file. The problem with this is that I would have to go through all of my code and add MagicLog() to everywhere that I have NSLog(), that seemed a bit to verbose for my liking.

After searching on the internet I found out that (rather obvious) NSLog runs over standard error. This means that you are able to simply redirect standard error to a file using the ANSI function freopen().


FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *restrict stream);


http://www.opengroup.org/onlinepubs/000095399/functions/freopen.html

Before we can save NSLog() to a file, we first have to find a place to save it. The best place to do this is the application’s documents folder. To get this you can use the following code snippet:


NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];


Once we have the documents folder, we need to give a name to the file. To make it easy for me I just name it “the date”.log :


NSString *fileName =[NSString stringWithFormat:@"%@.log",[NSDate date]];


To make this into a valid path, use the NSString method stringByAppendingPathComponent


NSString *logFilePath = [documentsDirectory stringByAppendingPathComponent:fileName];

The last step is to redirect stderr to this file


freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding],"a+",stderr);


To keep my code maintainable I keep all of this as a function, and I call it in my AppDelegate if I want to turn this functionality on.


- (void)redirectNSLogToDocumentFolder{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);

Getting the file.

Now that you have logged all the information you need, you will want to get this off of the device. Thankfully this is easy as well. Simply open the organiser in Xcode and select the device that is currently connected to your Mac.

A the bottom of the main pain there is an application section. Open the detail disclosure on the application you want to get the data from, and hit the little download button to the right of the Application Data package. You will be prompted to save this folder to your mac.

Warning:
Writing to the file system on the iPhone is slow, so this will effect the performance of your application. Therefore DO NOT ship an application with this in, or give it to people that can’t stand poor performance.

At first glance it would seem that the Cocoa Frameworks do this for you, and you would be right …. well kind of.

The issue is that by default most of these methods leave characters such as & = ? within a URL, as they are strictly speaking valid. The problem is that these characters have special meanings in a GET request, and will more than likely make your request in valid.

Luckily there is a function in Core Foundation that helps:

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CFStringRef CFURLCreateStringByAddingPercentEscapes (
   CFAllocatorRef allocator,
   CFStringRef originalString,
   CFStringRef charactersToLeaveUnescaped,
   CFStringRef legalURLCharactersToBeEscaped,
   CFStringEncoding encoding
);

What makes this function useful, is the legalURLCharactersToBeEscaped parameter. This will escape legal characters such as & ? = if they are supplied. This allows you to escape parameters using the following code.

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CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)parameter, NULL, CFSTR(":/?#[]@!$&’()*+,;="), kCFStringEncodingUTF8)

An example of when to use this, is Twitters Update status API. You can find that here http://apiwiki.twitter.com/Twitter-REST-API-Method%3A-statuses%C2%A0update

To update your status to the following:

This is my status

You would need to post up the following URL:

http://twitter.com/statuses/update.xml?status=This%20is%20my%20status

As this is such a common problem of mine, I have created a category on NSURL. This allows you to pass in a base URL and a parameters dictionary.

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+ (NSURL *)URLWithBaseString:(NSString *)baseString parameters:(NSDictionary *)parameters{
 
NSMutableString *urlString = [NSMutableString string];
 
//The URL starts with the base string
[urlString appendString:baseString];
 
NSString *escapedString;
 
NSInteger keyIndex = 0;
 
for (id key in parameters)
 {
 
//First Parameter needs to be prefixed with a ? and any other parameter needs to be prefixed with an &
if(keyIndex ==0)
{
escapedString = (NSString*)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
 (CFStringRef)[parameters valueForKey:key],
 NULL,
 CFSTR(":/?#[]@!$&’()*+,;="), 
kCFStringEncodingUTF8);
 
[urlString appendFormat:@"?%@=%@",key,escapedString];
[escapedString release];
}else{
 
escapedString = (NSString*)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, 
(CFStringRef)[parameters valueForKey:key],
 NULL, 
CFSTR(":/?#[]@!$&’()*+,;="),
 kCFStringEncodingUTF8);
 
[urlString appendFormat:@"&%@=%@",key,escapedString];
[escapedString release];
 
}
 
keyIndex++;
}
 
return [NSURL URLWithString:urlString];
 
}

Using a parameters dictionary keeps the code nice and clean, but beware, to use the category method above you still have to make sure that your keys, and the base URL are correctly encoded (no spaces or invalid characters !!!!!).

As we now have a category method to do all the hard work for us, to create the Twitter URL you just need to do the following:

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NSString *baseString=@"http://twitter.com/statuses/update.xml";
 
NSDictionary *dictionary=[NSDictionary dictionaryWithObjectsAndKeys:@"This is my status",@"status",nil];
 
NSURL *url=[NSURL URLWithBaseString:baseString parameters:dictionary];

And thats it. Obviously this category can be used for things other than twitter ….. if you really want to.

All animations triggered by the UIView class happen within a animation block.

To start an animation block you use the UIView Class method:

+ (void)beginAnimations:(NSString *)animationID context:(void *)context;


The animation ID is used in delegate call backs for such things as the beginning and end of animation blocks. The context is an additional piece of information that can be passed through.

As both of these parameters are optional, you comenly see:

[UIView beginAnimations:@"" context:NULL];


To commit these animations, and therefore end the animation block, you need to use the UIView class method:

+ (void)commitAnimations


So what types of animations can you do ? well quite a few.

You can animate views by:

• Changing their alpha
• Changing there size
• Changing there location

In a single animation block you can animate multiple views, and you are also able to nest animation blocks.

So lets do a common example. When a UITableViewCell is being edited you often want to make a UILabel’s (label) alpha change to 0 so it is hidden:

For those new to C programming:

(editing ? 0.0 : 1.0)


Is equivlant to:

if(editing)
{
0.0;
}else{
1.0;
}


So for the second example we also have a UILabel (label), that we want to grow when the animation code is run. We also want this animation to last 2 seconds, so the user can admire our work. In addition to this, we want the animation to “ease in”. This is known as the animation curve. The animation curves that are available are

• ease in (slow then fast)
• ease out (fast then slow)
• ease in and out (slow, fast, slow)
• linear (constant speed)

We would do this animation using the following animation block:

This is just a brief overview of the animations you can do using the UIView class, but it should be enough to get you started. The UIView methods also include delegate call backs for when an animation starts and end. For more information see Apple’s Documentation.

If the UIView class does not have what you need, you will probably need to use the Core Animation framework. While using this framework is not trivial, it is not as hard as using OpenGL (which is used commonly for 3D games), and you can build some fantastic animations using it.

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);