Re: Properties and bindings

[Andrew Merenbach]

On Sep 22, 2008, at 8:44 PM, D.K. Johnston wrote:

Thanks for the explanations: it does make some kind of sense now.



        @property(readonly) NSInteger myInt;

I can't do this in MyObject:

        self.myInt = 123;



        myInt = 123;

The reason I was looking at both forms is that I want the myInt property to be read-only, but I want the MyObject instance to be able to set it. If I do this: without generating a compiler error. And as you've all explained, I can't do this either: because the textfield value won't be changed. Is Jason's suggestion the best way to get around this problem?

Hi!

Check out this link -- <http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/Articles/chapter_5_section_4.html >. It examines what I believe to be similar to your issue. Basically, you can declare a property as readonly in the interface, but use either a subclass (shown on the page) or a class extension (new in Objective-C 2.0, but that shouldn't be a problem, since properties are, too) to override it in your implementation.

For example, leave it declared as readonly in your interface:

@interface MyClass : MySuperclass {
        NSInteger myInt;
}

@property (assign, readonly) NSInteger myInt;

@end

... then do this in your *implementation* file:

// this is your class extension
@interface MyClass ()
@property (assign, readwrite) NSInteger myInt;
@end


@implemtnation MyClass

// normal class stuff

@end

Cheers,
        Andrew

This would then have the effect of making a property readonly to all external classes, but readwrite to itself.

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