beginningi os part1-bobmccune

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Beginning iOS Development

Monday, March 19, 12



Beginning iOS DevelopmentAgenda

• Understanding the Tools

• Objective-C Crash Course

• Using Cocoa Touch


iOS SDK Tools


Xcode


Xcode•Apple’s IDE for creating Mac and iOS apps

•Provides visual front end to LLVM and LLDB

•Hub of development process:

Editing

Building

Refactoring

Debugging

API Doc Integration

UI Design

Testing

Model Design

Deployment

Project Configuration


iOS Simulator


•Device simulator, runs on your desktop

•Both iPhone and iPad (retina, non-retina)

•Faster code, build, test cycle

•Test behaviors: rotation, shake, multi-touch

•Easier testing of exceptional conditions

• iOS Simulator != iOS Device:

•No memory or CPU limits

•Not all APIs and capabilities available

iOS Simulator


Instruments


Instruments

• Dynamic tracing and profiling tool• Uses digital audio workstation-like interface• Large library of standard instruments

• Core Animation, Leaks, Automation, etc.

• The ultra geeky can build custom instruments


Hands-On Tour


Objective-C


Objective-C EssentialsAgenda

• Overview of Objective-C

• Understanding Classes and Objects

• Methods, Messages, and Properties

• Protocols


The old, new hotnessObjective-C

• Strict superset of ANSI C• Object-oriented extensions

• Additional syntax and types

• Dynamic, Object-Oriented Language:• Dynamic Typing

• Dynamic Binding

• Dynamic Loading


Creating Classes


The BlueprintCreating Classes

• Objective-C classes are separated into an interface and an implementation.• Usually defined in separate .h and .m files

•Defines the programming interface

•Can define object instance variables

•Defines the actual implementation code

•Implement one or more initializers to properly initialize an object instance


Defining the Interface@interface BankAccount : NSObject {}

@end

float accountBalance;NSString *accountNumber;

- (float)withDraw:(float)amount;- (void)deposit:(float)amount;


Defining the Implementation#import "BankAccount.h"

@implementation BankAccount

- (id)init { self = [super init]; return self;}

- (float)withdraw:(float)amount { // calculate valid withdrawal return amount;}

- (void)deposit:(float)amount { // record transaction}@end


Understanding the SyntaxDefining Methods

• Class methods

• Prefixed with a +

• Tied to class, not instance

• Instance Methods• Instance methods prefix with a -

• Modifies state of an object instance

- (NSString *)description;



• Class methods





- (BOOL)respondsToSelector:(SEL)aSelector;



• Class methods





+ (void)transitionWithView:(UIView *)view duration:(NSTimeInterval)duration options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion;


Talking to yourself

-(id)init { self = [super init]; if (self) { // do initialization } return self;}

• Methods have implicit reference to owning object called self

• Additionally have access to superclass methods using super

self and super


Working with Objects


Two-Stage Creation• NSObject defines class method called alloc

• Dynamically allocates memory for object

• Returns new instance of receiving class

BankAccount *account = [BankAccount alloc];

• NSObject defines instance method init

• Implemented by subclasses to initialize instance after memory for it has been allocated

• Subclasses commonly define several initializers

• alloc and init calls should always nested into single line

account = [account init];

BankAccount *account = [[BankAccount alloc] init];


Messages

• Methods are invoked by passing messages• Methods are never directly invoked

• Messages dynamically bound to method implementations at runtime

• Simple messages take the form:• [object message];

• Can pass one or more arguments:• [object methodWithArg1:arg1 arg2:arg2];

Communicating with Objects


Messaging an ObjectNSMutableDictionary *person =

[NSMutableDictionary dictionary];

[person setObject:children forKey:@"children"];

[person setObject:@"Joe Smith" forKey:@"name"];

NSString *address = @"123 Street";NSString *house = [address substringWithRange:NSMakeRange(0, 3)];[person setObject:house forKey:@"houseNumber"];

NSArray *children = [NSArray arrayWithObjects:@"Jack", @"Susie", nil];


Declared Properties


Declared Properties

• Most common methods we write are accessors

• Objective-C can automatically generate accessors

• Much less verbose, less error prone

• Highly configurable

• Declared properties are defined in two parts:

• @property definition in the interface

• @synthesize statement in the implementation

Simplifying Accessors


Declaring Properties

Attribute Impacts

nonatomic Concurrency

readonly/readwrite Mutability

strong/copy/weak/assign Storage

getter/setter API

@property (attributes) type variable;



Attribute Impacts




getter/setter API


@property (readonly) BOOL active;



Attribute Impacts




getter/setter API


@property (nonatomic, readonly) BOOL active;



Attribute Impacts




getter/setter API


@property (nonatomic, strong) NSDate *activeDate;



Attribute Impacts




getter/setter API


@property (readonly, getter=isValid) BOOL valid;


Defining the InterfaceDeclaring Properties

@interface BankAccount : NSObject

@property (nonatomic, copy) NSString *accountNumber;@property (nonatomic, strong) NSDecimalNumber *balance;@property (readonly, strong) NSDecimalNumber *fees;@property (getter=isCurrent) BOOL accountCurrent;

@end


Generating the AccessorsSynthesizing Properties

@implementation BankAccount

@synthesize accountNumber = _accountNumber;@synthesize balance = _balance;@synthesize fees = _fees;@synthesize accountCurrent = _accountCurrent;

@end


Accessing Properties• Generated properties are standard methods

• Accessed through normal messaging syntax

[object property];[object setProperty:newValue];

• Objective-C property access via dot notationobject.property;object.property = newValue;

Dot notation is just syntactic sugar. Still uses accessor methods. Doesn't get/set values directly.


Protocols


Object-Oriented ContractsProtocols

• Abstract methods to be implemented• Methods are not tied to a specific class

• Analogous to C# and Java interfaces

• Useful in defining:• Capturing similarities among classes that aren't

hierarchically related

• Declaring an interface while hiding its particular class

• Delegate callback methods


NSCodingDefining a Protocol

@protocol NSCoding

- (void)encodeWithCoder:(NSCoder *)aCoder;- (id)initWithCoder:(NSCoder *)aDecoder;

@end

* NSCoding defined in Foundation Framework


Conforming to the ContractAdopting a Protocol

@interface User : NSObject <NSCoding>

@property (nonatomic, copy) NSString *username;@property (nonatomic, copy) NSString *password;

@end


Conforming to the ContractAdopting a Protocol

@implementation User

-(id)initWithCoder:(NSCoder *)coder { if (self = [super init]) { self.username = [coder decodeObjectForKey:@"username"]; self.password = [coder decodeObjectForKey:@"password"]; } return self;}

-(void)encodeWithCoder:(NSCoder *)coder { [coder encodeObject:self.username forKey:@"username"]; [coder encodeObject:self.username forKey:@"password"];}

@end


Time to Code!


Using Cocoa Touch


Cocoa Touch

• Core framework for non-UI functionality

• Operating System Classes• threading, archiving, filesystem

• Collections• Common collection types: arrays, dictionaries, sets

• Networking support

• XML Processing

Foundation Framework


Cocoa Touch

• Framework for building iOS user interfaces

• User Interface Elements

• Tables, buttons, images, etc.

• Views and View Controllers

• Multitouch Event Handling

• High-level Drawing Routines

UIKit Framework


Model, View, ControllerUnderstanding MVC

Model View

Controller


The “V” in MVC

• Base class for iOS user interface components• Drawing and animation

• Layout and subview management

• Multitouch event handling

• Xcode’s Interface Builder used to build UI• Archived version of UI stored in XIB/NIB file

• Dynamically loaded at runtime by controller

• Can be created programmatically

UIView


The “C” in MVC

• The heart of every iOS app

• Provides the “glue code” between the model and view

• Responsible for managing the view hierarchy and lifecycle

• Key view lifecycle methods:

UIViewController

- (void)loadView;- (void)viewDidLoad;- (void)viewDidUnload;


Is view nil?

controller.view

View Controller

View loadView viewDidLoad

1) Overridden2) Loaded from NIB3) Return empty UIView

UIViewController: View Loading


View Unloading

• didReceiveMemoryWarning• Called by OS when low memory encountered

• If possible, will release controller’s view

• Can override, but must call super

• viewDidUnload invoked if root view released• Override to release anything that can be

recreated in loadView/viewDidLoad

Dealing with low memory conditions


Display-related Callbacks

viewWillAppear• Called immediately prior to being presented

viewDidAppear• Called upon view being added to window

viewWillDisappear• Called immediately before view is removed

from window or is covered by another viewviewDidDisappear

• Called after view is removed from window or is covered by another view


Wiring the View and View ControllerOutlets and Actions

• Provides metadata to Interface Builder to allow connections between objects

• IBOutlet

• Property reference to XIB/NIB objects

• Null-defined C macro

• IBAction

• Used by Interface Builder to determine available actions

• Void-defined C macro


Time to Code!


beginningi os part1-bobmccune

Technology

floatamount voiddeposit

interface bankaccount

import bankaccount

object instance nsstring

dening methodsunderstanding

float accountbalance

objects methods

syntax class methods