A couple of weekends ago I had the privelage of attending the “iPhone dev school” by robots and pencils, and taught by JR and Paul.

It was a fun weekend with a tonne of content packed in to 2 days. Here are a few of my notes from the course.

MVC

• Controller interacts with model.
• Controller interacts with view.
• Controller/View interaction occurs through the use of protocols and delegates.

Method Invocation

Greeting greeting = [[Greeting alloc] init];
[greeting greet:@"hello world" name:@"Mo"]
[greeting greet:@"hello world"]

@implementation Greeting
-(void)greet:(NSString *)title name:(NSString *)name
{
}
end

Header File

• .h -> header file that defines public interface of object

@protocol TempWeatherServiceDelegate <NSObject>
-(void)didFetchWeather:(Weather *)weather;
end

@interface TempWeatherService : NSObject
-(void)fetchWeather;
@property (nonatomic, weak) id <TempWeatherServiceDelegate> delegate;
end

Implementation File

• .m -> implementation file. this file defines the public and non public functions.

@implementation TempWeatherService

@synthesize delegate = _delegate;

-(void)fetchWeather
{
  Weather *weather = [[Weather alloc] init];
  weather.currentTemperature = -20;
  [self.delegate didFetchWeather:weather]
}

Protocols and Delegates

• Controller assigns itself as the view’s delegate.
• View can only have a single delegate.
• View forwards screen interactions to it’s delegate.
• the protocol is the contract that the controller must implement in order to receive calls of specific screen interactions.
• the view has no intimate knowledge of its delegate, only the contract (protocol) defined between it and its delegate.
• protocols are used to achieve polymorphic behaviour.
• allows for non-blocking calls. interesting asynchronous programming model.

TempWeatherService service = [[TempWeatherService alloc] init];
service.delegate = self;
[service fetchWeather]

Notifications (event aggregator)

• NSNotifications can go to any number of subscribers.

[NSNotificationCenter defaultCenter]
-(void)addObserver:(id)observer selector:(SEL)methodToCallIfSomethingHappens name:(NSString)name object:(id)sender