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iOS Development for Non-Engineers

Jeremy Bridon

Core S2 - Core Software Solutions

www.cores2.com

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What you really need

  • Macintosh
  • Dev. License
  • XCode (4+)
  • iOS SDK (bundled with XCode)
  • Device (good for hardware testing)

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Language & Framework:

intimate relationship

  • Development Language: C and Objective-C
    • Note: C++ is "supported"
  • Framework?
    • Base: NSObject, NSString, etc.
    • Features: Foundation, UIKit, CoreAnimation, etc.
  • What you should know:
    • Obj-C design implications
    • View hiarchy, UIView, UIViewController
    • Protocols & Delegates

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Caveats of Objective-C

  • It is a PURE extension of C, unlike C++
  • Member-function calls are the same, conceptually
    • C++: int Data = MyObj.GetData()
    • ObjC: int Data = [MyObj GetData];
  • Argument list is more verbose
    • C++: MyFunc(a, b, c);
    • ObjC: [MyFunc: a withB: b withC: c];
  • All objects are on the heap
  • Protocols / delegates!

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Protocols & Delegates

  • Preview: Similar to C callback functions / function pointers

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View-Hierarchy

  • Views are built as a tree-graph (pyramid)
  • Roots are generally UIViewController
    • Globally: all owned by UIWindow (one per application)
    • Is essentially a container
  • Sub-objects derive from UIView
    • Caveat: Everything is rendered, these aren't "windows" of views
    • Can have custom-rendering, by overloading "renderFrame" member-function

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View-Hierarchy

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Demo!

View with sub-views

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Protocols & Delegates

  • GUI commonly needs pseudo-asynchronous event callbacks
    • If user presses button, why should the OS block?
  • Some call-backs are specialized, giving back specific data types
    • Button's "ButtonPressed..." is different than Lists's "SelectedItem..."
  • How to abstract this? Classes don't overload or derive! That's NASTY
    • Insteads, implement a protocol!
    • Note: Protocol is the formal definition, delegate are the callback function prototypes

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Protocol Example

Your UIViewController object needs to catch GPS update data. How?

  1. Register this instance with the GPS data
  2. Implement the protocol:

CoreLocationControllerDelegate

  • Recieve data, when ready, through delegate functions:

@protocol CoreLocationControllerDelegate �@required�- (void)locationUpdate:(CLLocation *)location;�- (void)locationError:(NSError *)error;

@end

​

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Demo!

1. Formal protocol implementation

Example: Catch user events

2. Casual delegate implementation

Example: timers