Alex Rivera | Logout

Lazy instantiation in Objective-C

Asked 2012-08-02T00:44:46.050
28

I understand that all properties start out as nil in Objective-C and that sending a message to nil does nothing, therefore you must initialize using [[Class alloc] init]; before sending a message to a newly created property.

However, what about if I'm not sending messages to this property or if I set the property using self.property = something? Do I need to alloc init in these cases as well? Also, do UI properties start out as nil as well, such as a UILabel property that you drag out from your storyboard? Do these need alloc init?

objective-c properties initialization lazy-initialization alloc
Edit
Report

1 Answer

2

I don't have experience with Storyboards but I know that when you create objects via a xib file all objects are properly instantiated when you tell a view controller to use a xib file. So you need not worry about alloc/initing those objects in code.

Regarding using self.property = <something>, it depends on what something is. If something is any sort of existing object you need not do the alloc init on that object as the self.property = ... syntax calls the property's setter method which will retain, copy, assign, etc. the new value to the property appropriately.

Now any sort of existing object can be an alloc/init'ed object, or an autoreleased object obtained from a convenience method (NSString's stringWithFormat: for example).

As Kaan Dedeoglu pointed out, the self.property = ... syntax points (and retains) the ivar to the object in memory, and it is up to you to initialize that object if it isn't already instantiated.

answered 2012-08-02T01:01:08.587

Your Answer