Use NSNumber to store numbers in NSArrays and NSDictionaries: @123

int myValue = [theNumber intValue];

NSNumber *number = @(a + 1);

Blocks allow you to store chunks of code in variables and call them later

You must copy a block to be able to access it after a method

In order to modify a variable, that is declared outside of the block, inside the block you must mark the variable with the __block keyword

A frame rectangle is defined relative to its superview

Bounds rectangle is the view's position and size relative to its own coordinate space

for (NSString* key in dictionary) { NSObject* theValue = [dictionary objectForKey:key]; [aProduct setValue:theValue forKey:key]; }

If you try to set a value for a key that does not exist in your class, the key-value coding system will throw an exception because the runtime won’t know where to store the value

Notifications come with a special aps dictionary which contains information about how the push notification should be presented