On Jan 22, 2013, at 1:28 PM, Andy Lee <ag...@mac.com> wrote: > On Jan 22, 2013, at 2:19 PM, Charles Srstka <cocoa...@charlessoft.com> wrote: > >> On Jan 22, 2013, at 12:58 PM, Andy Lee <ag...@mac.com> 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 _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
