完全看文档和视频这里怎么就错呀？？？？？

Undefined symbols for architecture i386:

  "_ACAccountTypeIdentifierTwitter", referenced from:

      -[PF_Twitter getLocalTwitterAccountAsync] in Parse(PF_Twitter.o)

  "_OBJC_CLASS_$_ACAccountStore", referenced from:

      objc-class-ref in Parse(PF_Twitter.o)

  "_OBJC_CLASS_$_SLComposeViewController", referenced from:

      objc-class-ref in Parse(PF_Twitter.o)

  "_OBJC_CLASS_$_SLRequest", referenced from:

      objc-class-ref in Parse(PF_Twitter.o)

  "_SLServiceTypeTwitter", referenced from:

      -[PF_Twitter getAccessTokenForReverseAuthAsync:localTwitterAccount:] in Parse(PF_Twitter.o)

      -[PF_Twitter getLocalTwitterAccountAsync] in Parse(PF_Twitter.o)

ld: symbol(s) not found for architecture i386

clang: error: linker command failed with exit code 1 (use -v to see invocation)