How to set up clang formatter

Step 1:
Install alcatraz (http://alcatraz.io). Alcatraz is a package manager for Xcode.
How to install? Simply run:
curl -fsSL https://raw.github.com/supermarin/Alcatraz/master/Scripts/install.sh | sh

Step 2:
In Xcode, go to Window -> Package manager.
Search for clangformat.
Click on the folder/briefcase like icon on the left, to install clangformat plugin.
It installs pretty quickly and it might not tell you that it is installed. Do not tap on the folder/briefcase icon again, it will uninstall the plugin.
Close and re-open the package manager, search for clangformat, folder/briefcase like icon should be blue now. That'd indicate that clangformat plugin is now installed.
Restart Xcode
You can read more about clangformat plugin here: https://github.com/travisjeffery/ClangFormat-Xcode . It is based on clang-format.

Step 3:
In Xcode, go to Edit -> Clang Format. Pick "File".
This will ensure that auto-formatter uses our custom formatting preferences file located at apps/shopkick/iphone/Shopkick/.clang-format and lib/iphone/.clang-format.
We're following a slight variation of LLVM coding style.

Step 4:
In Xcode, go to Edit -> Clang Format. Pick "Enable format on save".
This will auto format your code when you save it.
When you are touching the code that hasn't been auto-formatted before, it is recommended that you auto-format it first and place the diff in a separate commit. Your code reviewer will thank you.