Xcode "Undefined symbols for architecture i386" Error without any change on code, all of a sudden

I get the Undefined symbols for architecture i386. Here's what I did:

1. I checked many times for miswriting .h .m extensions. They are true.

2. I deleted Framework Search Paths and then wrote "./" being defined as "Recursive" as it was provided as a solution but it did not work also.

3. Can it be related with Architecture settings, it is now set as $(ARCHS_STANDARD).

   Undefined symbols for architecture i386:
   "_OBJC_CLASS_$_EMDenemeSinaviCell", referenced from:
        __TFC8EduMobil24EMAssesmentEvaluationNEW9tableViewfS0_FTCSo11UITableView21cellForR        owAtIndexPathCSo11NSIndexPath_CSo15UITableViewCell in         EMAssesmentEvaluationNEW.o
   ld: symbol(s) not found for architecture i386
   clang: error: linker command failed with exit code 1 (use -v to see invocation)
   
   

4. When i change the current Cell Class i am using to another Cell Class it does not give any error. But it gives the following warning:

   file was built for i386 which is not the architecture being linked (x86_64): 
   
   

How can I solve this error?