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Re: How to avoid warning?
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Re: How to avoid warning?


  • Subject: Re: How to avoid warning?
  • From: Andy Lee <email@hidden>
  • Date: Tue, 22 Jan 2013 14:28:01 -0500

On Jan 22, 2013, at 2:19 PM, Charles Srstka <email@hidden> wrote:

> On Jan 22, 2013, at 12:58 PM, Andy Lee <email@hidden> wrote:
>
>> // Or this also works (protocol).
>> @protocol AvoidCompilerWarning
>> - (id)initWithArg:(id)arg;
>> @end
>
> Really, a protocol is what you ought to be doing. Make a protocol with -initWithManager: in it, and then make all the classes that might get passed to this method comply with your protocol. Then, do this:
>
> if ([myClass conformsToProtocol:@protocol(MyProtocol)])
> 	myObj = [[myClass alloc] initWithManager:sel]];
> else
> 	myObj = [[myClass alloc] init];
>
> The advantage to this method is a simple one: Suppose some random class happens to implement a method named -initWithManager:, but that method has nothing to do with your -initWithManager: other than a coincidental title, and takes a completely different type of object. Your original code will result in unpredictable behavior in this case (and probably throw an exception leading to a crash). If you use a protocol, you'll know not just that the method responds to something named -initWithManager:, but that it's *your* -initWithManager:

Makes sense, especially since it sounds like you have enough control of the class to declare it as conforming to the protocol.

To be extra fail-safe, you might want to perform a cast to be sure the right initWithManager: gets called:

if ([myClass conformsToProtocol:@protocol(MyProtocol)])
	myObj = [(id <MyProtocol>)[myClass alloc] initWithManager:self];
else
	myObj = [[myClass alloc] init];

--Andy

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  • Follow-Ups:
    • Re: How to avoid warning?
      • From: Uli Kusterer <email@hidden>
    • Re: How to avoid warning?
      • From: Charles Srstka <email@hidden>
References: 
 >How to avoid warning? (From: Dave <email@hidden>)
 >Re: How to avoid warning? (From: Jens Alfke <email@hidden>)
 >Re: How to avoid warning? (From: Dave <email@hidden>)
 >Re: How to avoid warning? (From: Jens Alfke <email@hidden>)
 >Re: How to avoid warning? (From: Andy Lee <email@hidden>)
 >Re: How to avoid warning? (From: Charles Srstka <email@hidden>)

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