Why do I change the code in xcode inside, not on the simulator corresponding operation

Why do I change the code in xcode inside, not on the simulator corresponding operation.
With the sdk is 5.0, the virtual machine can be, on the virtual machine sdk is 5.1.
Reply:
Before running clean look: command + shift + k
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product-> clean
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Solved, I was restored to the simulator. The above two may say may be required.
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I also encountered the same problem, but my question is if the simulator is the English language can be, if the Chinese language, there is no change to modify the code, you restore the simulator, then the simulator becomes English language, and will will not be the same problem with me, you try to see into Chinese language
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Can be changed to English