Comments on: Objective-C: Alternative Use of Properties?

By: john

john — Sun, 17 Aug 2008 01:41:06 +0000

Comments are closed on this post. You can comment on this same post which has been moved to the iPhone Developer Tips blog: http://iphonedevelopertips.com/objective-c/alternative-use-of-properties.html

By: stompy

stompy — Thu, 14 Aug 2008 19:05:46 +0000

I think it is because properties do not need to be directly tied to individual ivars.

How about this as an example

@interface SomeClass : NSObject
{
NSString *firstName
NSString *lastName
}
@property (copy, readwrite) NSString *firstName;
@property (copy, readwrite) NSString *lastName;
@property (readonly) NSString *fullName;

@end

Now, in the implementation, you explicitly define the getter which operates on the other properties.

- (NSString *)fullName
{
NSString *retString;
retString = [NSString stringWithFormat:(@"%@ %@", firstName, lastName)];
}

You could have used self.firstName and self.lastName above.

By: john

john — Fri, 25 Jul 2008 17:11:46 +0000

Thanks Paul. What’s kind of intriguing about this approach, and the example that I was looking at, was that the method used in this manner had nothing to do with the instance variables in the class definition. The method returned a reference to a UIImage based on a specific string format (which defined the size of the image to retrieve).

This is cool for a few reasons. First, with the ‘readonly’ value specified in the property definition, there is only a getter required/implied. Second, the method can be accessed using dot syntax.

By: Paul C

Paul C — Fri, 25 Jul 2008 16:48:46 +0000

Hey John, I remember from reading about properties the other day that the default value for a property directives is @dynamic. So, if you declare a property in your interface, but do not specify @synthesize in your implementation it will default to dynamic and expect you to implement a getter/setter corresponding to the @property you’ve defined in the implementation or at runtime.