아이폰 앱 개발 팁(3) : Stanford Lecture #3

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> Stanford Lecture #3

* Superclass methods

Implicit variable, "self" : Like "this" in Java and C++

Superclass methods, "super"

* Object Creation

1st step : allocate memory to store the object

2nd step : initialize object state

+ alloc : class method(cf. dealloc for destruction)

- init : instance method

Person *person = nil;

person = [[Person alloc] init];

* Multiple init methods

- (id)init;

- (id)initWithName:(NSString *)name;

- (id)initWithName:(NSString *)name age:(int)age;

- (id) init {

return [self initWithName:@"No Name"];

}

- (id) initWithName:(NSString *)name {

return [self initWithName:name age:0];

}

* Reference Counting

As long as retain count is greater than zero, object is alive and valid.

+alloc and -copy create objects with retain count == 1.

-retain increments retain count.

-release decrements retain count.

When retain count reaches 0, object is destroyed.(-dealloc method invoked automatically.)

You only deal with alloc, copy, retain, release.

You never call dealloc explicitly in your code except for "[super dealloc]".

* Returning a newly created object

- (NSString *) fullName {

NSString *result;

result = [[NSString alloc] initWithFormat:@"%@ %@", firstName, lastName];

[result autorelease];

return result;

}

The result is released, but not right away. Caller gets valid object and could retain if needed.

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