This document discusses object creation and memory management in Objective-C on iPhone apps. It covers the two-step process of allocating memory and initializing objects. Classes can define multiple initialization methods. Reference counting is used to manage object lifetimes - objects are retained, released, and deallocated automatically. iPhone apps differ from other platforms in only allowing one app and window at a time, and having limited system resources.

1. iPhone Apps A Closer Look

2. More about Obj-C Object Creation Two step process allocate memory initialize object + alloc class method that allocates memory for the object - init instance method to complete initialization

3. Creating Objects Person *person = nil; person = [[Person alloc] init]; OR Person *person = [[Person alloc] init]; - (id)init { // allow superclass to initialize its state first if (self = [super init]) { age = 0; name = nil; } // do other initialization… return self }

4. Multiple init methods Classes may define multiple init methods - (id)init; - (id)initWithName:(NSString *)name; - (id)initWithName:(NSString *)name age:(int)age; person = [[Person alloc] init]; [person setName:@”MyName”]; [person setAge:24]; // Use ‘person’ object // What is next ? [person release];

5. Reference counting Every object has a “ retainCount ” as long as retainCount is > 0 ,object is alive +alloc and - copy create objects with retainCount 1 -retain increments retainCount -release decrements retainCount When retainCount reaches 0 , object is destroyed -dealloc method invoked

6. Object deallocation #import "Person.h" @implementation Person -(void)dealloc { // Do any cleanup that’s necessary // when we’re done, call super to clean us up [super dealloc]; } @end You never call dealloc explicitly in your code You only deal with alloc , copy , retain , release to manage an object’s lifetime

7. iPhone v/s other patforms Only one application at a time Only one window Limited Access Limited Response Time Carefully craft Apps Make sure data is not lost when user quits Limited System Resources RAM 128MB, Capacity 8GB ~70MB left for user applications No swap file

8. iPhone v/s other patforms . . . What you can ? Photo Library Camera Location Services Address Book Accelerometer Many more . . .

9. ANATOMY OF AN XCODE PROJECT Main Components Classes Other Sources Resources Framework Product Target