Re: protocol and properties
Re: protocol and properties
- Subject: Re: protocol and properties
- From: "Stephen J. Butler" <email@hidden>
- Date: Sun, 28 Nov 2010 03:26:02 -0600
On Sun, Nov 28, 2010 at 3:15 AM, Martin Hewitson
<email@hidden> wrote:
> It 'works' for me too, I just warnings from Xcode. Anyway, I'll check in case I made a typo or something.
I don't get any warnings.
> On 28, Nov, 2010, at 9:50 AM, Stephen J. Butler wrote:
>
>> On Sun, Nov 28, 2010 at 2:15 AM, Martin Hewitson
>> <email@hidden> wrote:
>>> Suppose I have a formal protocol which defines a method:
>>>
>>> - (NSArray*)objects;
>>>
>>> Then I implement a class which implements this protocol. To do that I make a property:
>>>
>>> @property (nonatomic, readwrite, retain) NSArray * objects;
>>>
>>> and put the appropriate synthesize statement in the implementation.
>>>
>>> I get compiler warnings that this class doesn't implement the protocol. It seems it doesn't take the synthesized getter as being an implementation of the -objects method.
>>>
>>> I also tried explicitly adding the implementation, but the warning remains:
>>>
>>> - (NSArray*) objects
>>> {
>>> return objects;
>>> }
>>>
>>> Am I doing something wrong here, or is it not possible to use a property to satisfy a protocol?
>>
>> Works for me:
>>
>>
>> #import <Foundation/Foundation.h>
>>
>> @protocol Bar
>> - (NSArray*) objects;
>> @end
>>
>> @interface Foo : NSObject < Bar > {
>> NSArray *objects;
>> }
>> @property (nonatomic, readwrite, retain) NSArray *objects;
>> @end
>>
>> @implementation Foo
>> #if 0
>> - (NSArray*) objects { return objects; }
>> - (void) setObjects:(NSArray*)o {
>> [o retain];
>> [objects autorelease];
>> objects = o;
>> }
>> #else
>> @synthesize objects;
>> #endif
>> @end
>>
>> int main (int argc, const char * argv[]) {
>> NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
>>
>> Foo *f = [[[Foo alloc] init] autorelease];
>> id< Bar > b = f;
>>
>> f.objects = [NSArray arrayWithObjects:@"one",
>> @"two", @"three", nil];
>> NSLog( @"objects = %@", [b objects] );
>>
>> [pool drain];
>> return 0;
>> }
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Martin Hewitson
> Albert-Einstein-Institut
> Max-Planck-Institut fuer
> Gravitationsphysik und Universitaet Hannover
> Callinstr. 38, 30167 Hannover, Germany
> Tel: +49-511-762-17121, Fax: +49-511-762-5861
> E-Mail: email@hidden
> WWW: http://www.aei.mpg.de/~hewitson
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
>
>
>
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