This issue is not a major issue but has certainly made the process consume more time. When I build my application, indexing fails in one and only one file (.m file if it matters).
There is not intelligence, no color on global variables and most of the code except for important keywords are black in color. Since there is no intelligence, whenever I need to make changes, I have to see other files for doing the changes.
I found solution to my question. Actually a localized file of that file was being created in en.proj folder, where indexing failed. So, I just copied that file into project main folder and deleted it from en.proj folder. It works fine now. I can see everything indexed.