在Objective-C中，有没有办法指定希望@selector（）使用哪个选择器的定义？

Xcode 4 is giving me (rather unhelpful) errors about "unimplemented selector 'xxx'" when I try to use @selector(xxx) with any method not actually defined in the same source file. The error goes away (at least for the project build) if I set the LLVM compiler warning, "Multiple Definition Types for Selector" to "No". (This is the iOS default, but for my project it had been enabled.) Xcode 4 is giving me (rather unhelpful) errors