MailCore Errors IOS

I try to use MailCore in my project, but I get these error:

Undefined symbols for architecture armv7:
  "_MailCoreEnableLogging", referenced from:
      -[ImapSync run] in ImapSync.o
  "_OBJC_CLASS_$_CTCoreMessage", referenced from:
      l_OBJC_$_CATEGORY_CTCoreMessage_$_CTCoreMessageBuisnessMail in CTCoreMessage+BuisnessMail.o
  "_OBJC_IVAR_$_CTCoreMessage.myFields", referenced from:
      -[CTCoreMessage(CTCoreMessageBuisnessMail) libetpanDateTime] in CTCoreMessage+BuisnessMail.o
      -[CTCoreMessage(CTCoreMessageBuisnessMail) senderDate] in CTCoreMessage+BuisnessMail.o
  "_OBJC_CLASS_$_CTCoreAccount", referenced from:
      objc-class-ref in AttachmentDownloader.o
      objc-class-ref in ImapSync.o
  "_MailCoreDisableLogging", referenced from:
      -[ImapSync run] in ImapSync.o
  "_IfTrue_RaiseException", referenced from:
      -[ImapFolderWorker fetchFrom:to:seqDelta:syncingNew:progressOffset:progressTotal:alreadySynced:] in ImapFolderWorker.o
ld: symbol(s) not found for architecture armv7

but all of these methodes are there, I can see them in the MailCoreProject!

I hope someone can help me!

Solution

First, I would check if you have added libMailCore-ios.a to your list of "Linked Frameworks and Libraries".

If so, then the problem could be that the MailCore project was compiled for one device while your main project was compiled for a different device. For instance,

the MailCore project was compiled for simulator ... the symbols of MailCore were generated for x86 architecture
your main project was compiled for real iOS device ... so the linker was looking for MailCore symbols for armv7 architecture
Thus, the linker complained, symbols for armv7 architecture not found

To solve the problem, rebuild the MailCore subproject (build-clean and build) with the same device (or same simulator) as your main project.