(1) OC advanced programming and oc Advanced Programming

(1) OC advanced programming and oc Advanced Programming
Do Loop:

Always do something until a condition is not true

Continue:

Skip this loop and enter the next one, while break jumps out of the entire loop.

Conditional operators:

This figure means that whenageGreater than or equal18,testIs9Otherwise10. The condition operators above are equivalentif-elseExpression

Restrictions:

• nonatomic,atomic-- Atomic: Only one thread can be accessed at a time. If multiple threads/tasks are accessed at the same time, queuing is required, which affects program efficiency. Therefore, "non-atomicnonatomicBut it is more secureatomicLow.

• copy-- A copy will be copied, without affecting the original data

• retain-- The reference count of the object is increased by 1.

• strong,weak-- It appears only after 4.0, with strong references and weak references.strongEquivalentretain,weakEquivalentassign,weakIt can only be used on object data.

• assign-- It is generally used to modify basic data types, such as int and float.

• readonly-- Read-only, cannot be modified

- (void)viewDidLoad {    [super viewDidLoad];        self.title = @"Two";    self.bgImageView.image = [UIImage imageNamed:@"bg2"];    }