By default, the setting to update the Xcode project file is turned on in Swiftify for Xcode. So when you convert the Objective-C with the Xcode project file selected as shown below:
The Xcode project file is automatically updated by the converter and the links to the old Objective-C files are replaced with links to the new Swift files.
In certain cases, you may not want the Xcode project file to be updated automatically.
For example, your workspace may contain multiple Xcode projects, but you may not want the converter to touch any other project except for the project you are working on.
To disable the updating of any particular Xcode project file, you can manually unselect the Xcode project file for a particular project in the project tree:
To disable processing of all Xcode project files by default, you can un-check this option under Preferences (⌘+,) => Converter and toggle the corresponding checkbox: