[UIViewController ttAddNavigatorController:]: unrecognized selector 的错误问题

今天在工程里集成了Three20,一切都很顺利，运行时却抱[UIViewController ttAddNavigatorController:]: unrecognized selector异常。

经过查找资料：

http://developer.apple.com/library/mac/#qa/qa1490/_index.html

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A: Why do I get a runtime exception of "selector not recognized" when linking against an Objective-C static library that contains categories?

The "selector not recognized" runtime exception occurs due to an issue between the implementation of standard UNIX static libraries, the linker and the dynamic nature of Objective-C. Objective-C does not define linker symbols for each function (or method, in Objective-C) - instead, linker symbols are only generated for each class. If you extend a pre-existing class with categories, the linker does not know to associate the object code of the core class implementation and the category implementation. This prevents objects created in the resulting application from responding to a selector that is defined in the category.

To resolve this issue, the target linking against the static library must pass the -ObjC option to the linker. This flag causes the linker to load every object file in the library that defines an Objective-C class or category. While this option will typically result in a larger executable (due to additional object code loaded into the application), it will allow the successful creation of effective Objective-C static libraries that contain categories on existing classes. Follow these steps to pass -ObjC to the linker:

1. In Xcode, double-click the target's name under "Targets" in the Project window.

2. Choose the Build pane from the ensuing Info window.

3. Scroll down to the Other Linker Flags build setting under the Linking collection and set its value to -ObjC.

在工程设置里加上 -ObjC 后， 问题搞定