iphone:Urban飞艇libUAirship-1.1.1。发生错误

我正在我的应用程序中实现推送通知（城市飞艇）。我已经编写了代码，还添加了必要的框架，包括libUAirship-1.1.1.a，但它显示了以下错误

   Undefined symbols for architecture i386:
  "_UTTypeCreatePreferredIdentifierForTag", referenced from:
      +[UA_ASIHTTPRequest mimeTypeForFileAtPath:] in libUAirship-1.1.1.a(UA_ASIHTTPRequest.o)
  "_UTTypeCopyPreferredTagWithClass", referenced from:
      +[UA_ASIHTTPRequest mimeTypeForFileAtPath:] in libUAirship-1.1.1.a(UA_ASIHTTPRequest.o)
  "_kUTTagClassFilenameExtension", referenced from:
      +[UA_ASIHTTPRequest mimeTypeForFileAtPath:] in libUAirship-1.1.1.a(UA_ASIHTTPRequest.o)
  "_kUTTagClassMIMEType", referenced from:
      +[UA_ASIHTTPRequest mimeTypeForFileAtPath:] in libUAirship-1.1.1.a(UA_ASIHTTPRequest.o)
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

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我无法理解为什么会产生此错误。

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