duplicate line xcode
Go to : /Applications/Xcode.app/Contents/Frameworks/IDEKit.framework/Resources
$ sudo nano IDETextKeyBindingSet.plist
ADD THIS TO END OF FILE BEFORE DICT END TAG
<key>Customized</key>
<dict>
<key>Duplicate Current Line</key>
<string>selectParagraph:, delete:, undo:, moveRight:, yankAndSelect:</string>
</dict>
restart Xcode and go to Preferences-> Key bindings and search for Duplicate Current Line
This will work with multiple lines and doesn't mess with clipboard
taken from:
https://stackoverflow.com/questions/10266170/xcode-duplicate-line/41121405#41121405