Re: How to avoid warning?
Re: How to avoid warning?
- Subject: Re: How to avoid warning?
- From: Charles Srstka <email@hidden>
- Date: Tue, 22 Jan 2013 13:34:21 -0600
On Jan 22, 2013, at 1:28 PM, Andy Lee <email@hidden> wrote:
> 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
That's a good fix. In addition to being more fail-safe, that also lets clang and Xcode know exactly what you intend here, so that if you decide someday to do something like rename the initWithManager: method using Xcode's Refactor feature, it should get this invocation of the method as well.
Charles
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