gistfile1.txt

Protocol
------------

Protocol in Objective-C is like interface in Java
Apple tends to favor using subclasses than protocol
NSObject is a class but also a protocol

Category
------------

Categories not allow to add properties to classes

@interface CCBird(<Category Name>)
@end

Associate Object
-----------------

An object that is associated with another object

Memory
---------

Automatic referece counting
Weak reference

When using nonatomic, strong is also implied
Child pointing to a parent should always use a weak reference
When a property is synthesized, it will call copy on the property
When calling copy on a mutable object, we get back an immutable object

NSString is a cluster class (having multiple definitions of it)
assign is usually used with primitive

@autoreleasepool

Rule of thumb
--------------

Stays at the highest level of abstraction as possible.
UIKit > Core Animation > Core Graphics > OpenGL ES (UIKit is the highest level of abstraction)
Parsing string is expensive in iOS

Drawing distances are measured in points
Screen dimensions are measured in pixels
Retina screen: 2 pixels make 1 point
Frame: size and location of a view in its superview's coordinate system
Bounds: size of the view and its content origin in its local coordinate system
Transform: affine transform applied to the view's coordinate system relative to the view's center property.
convertPoint:(CGPoint *)srcPoint fromView:(UIView *)srcView
setNeedsLayout: will percolate down to child views
Avoid using drawRect for performance sake
CGRect is a struct not an object so we don't need a * when declaring it
UIScreen's application frame is everything excluding the 20px of the navigation bar where as bounds gives us everything.
Application frame is different between iOS 6 and 7
self.view will create a view
Delegate should be a weak reference because it has a pointer to the view controller
[[NSNotification defaultCenter] removeObserver:self]

Main Thread
---------------

UI Event Run Loop
NSThread
Threads are expensive (512k of stack / 90 microseconds creation time)
Grand Central Dispatch is much better than Threads
NSOperationQueue
@synchronized
typeof(self)

Core Animation Framework
-------------------------

Every UIView has a layer
Cocoa supports layers but they're not turned on by default

Animation
----------

CGRect is an animatable property

Forward declaration
UIRefreshControl