This plugin written for Xcode 8's new plugin infrastructure uses Clang's libclangFormat library to format code according to a .clang-format file.
Open the app, select a predefined style, or open the .clang-format file from your project:
Then, use the Format Source Code command in Xcode's Editor menu:
Due to macOS Sandboxing restrictions, this Plugin behaves slightly differently compared to the command line clang-format command: It always uses the style selected in the configuration app, and will not use the nearest .clang-format file on disk.