【原】Automatic Reference Counting(ARC) properties learning

1、With ARC, you should use strong instead of retain and weak instead of assign  when defining the properties.

@interface Person : NSObject
@property (nonatomic, strong) NSString *firstName;
@property (nonatomic, strong) NSString *lastName;
@property (nonatomic, strong) NSNumber *yearOfBirth;
@property (nonatomic, strong) Person *spouse;
@end

2、ARC forbids 'dealloc','release','autorelease' key words, these words shouldn`t be explicitly invoked!

For instance,[super dealloc] [str release] are not permitted.

3、When you use [[AClass alloc] init], you don`t need to release it.

- (void)takeLastNameFrom:(Person *)person {

    NSString *oldLastname = [self lastName];

    [self setLastName:[person lastName]];

    NSLog(@"Lastname changed from %@ to %@", oldLastname, [self lastName]);
//oldLastname will stay alive until NSLog is runned
}

4、