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Re: Compiler can't find method declared in protocol
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Re: Compiler can't find method declared in protocol


  • Subject: Re: Compiler can't find method declared in protocol
  • From: Andy Lee <email@hidden>
  • Date: Tue, 18 Dec 2012 15:59:02 -0500

Great catch! And it just so happens this pitfall is mentioned in Mike Ash's latest Friday Q&A:

<http://mikeash.com/pyblog/friday-qa-2012-12-14-objective-c-pitfalls.html>

("Missing Method Argument")

--Andy

On Dec 18, 2012, at 11:46 AM, BlueBoy <email@hidden> wrote:

> You're missing the first argument name in the protocol method...
>
> - (void)tokenControl:(RPTokenControl*) <missingArgument>
>        renameToken:(NSString*)token ;
>
>
>
>
>
> On 18 Dec 2012, at 14:31, Jerry Krinock wrote:
>
>> I am so stumped as to why llvm cannot see the declaration of a method in a protocol that I have reproduced the issue in a small test project.  An error or warning occurs in the last line of the following code, where I send the message to a delegate which is declared to implement the protocol.
>>
>> If ARC is on, I get this the error:
>> No visible @interface for 'NSObject<RPTokenControlDelegate>' declares the selector 'tokenControl:renameToken:'
>>
>> If ARC is off, it instead appears as a warning:
>> Instance method '-tokenControl:renameToken:' not found (return type defaults to 'id')
>>
>> In my real project, which is non-ARC, if I ignore the warning, the code runs OK.
>>
>> Thank you for answering what must be a simple question.
>>
>> Jerry Krinock
>> D
>> *******  JunkLib.h **********************************************
>>
>> #import <Foundation/Foundation.h>
>>
>> @protocol RPTokenControlDelegate ;
>>
>> @interface RPTokenControl : NSObject {
>>   NSObject <RPTokenControlDelegate> * m_delegate ;
>> }
>>
>> @property (assign) NSObject <RPTokenControlDelegate> * delegate ;
>>
>> @end
>>
>>
>> *******  JunkLib.m **********************************************
>>
>> #import "JunkLib.h"
>>
>> @protocol RPTokenControlDelegate
>>
>> - (void)tokenControl:(RPTokenControl*)
>>        renameToken:(NSString*)token ;
>>
>> @end
>>
>> @implementation RPTokenControl
>>
>> - (IBAction)renameSelectedToken:(NSMenuItem*)sender {
>>   [[self delegate] tokenControl:self
>>                     renameToken:@"junk"] ;  // ERROR!!
>> }
>>
>> @end
>>
>>
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References: 
 >Compiler can't find method declared in protocol (From: Jerry Krinock <email@hidden>)
 >Re: Compiler can't find method declared in protocol (From: BlueBoy <email@hidden>)

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