Re: protocol and properties
Re: protocol and properties
- Subject: Re: protocol and properties
- From: Martin Hewitson <email@hidden>
- Date: Sun, 28 Nov 2010 10:26:41 +0100
OK, then it seems I didn't do something fundamentally wrong. Probably a stupid mistake somewhere.
Thanks again!
Martin
On 28, Nov, 2010, at 10:26 AM, Stephen J. Butler wrote:
> 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
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>>
>>
>>
>>
>>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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