Question

There is a Duplicate command in the Edit Menu (with a default shortcut of ⌘D), but it is (as Halley pointed out) meant for duplication in the Interface Builder part of Xcode.

So, how do you (easily) duplicate a line in Xcode 4?

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Related question (with a working answer) for Xcode 3 … and which does not work for Xcode 4.

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Why not just copy & paste?

Because it is tedious and entails too much hand-acrobatics:

either (1): moving to line beginning and then pressing ⇧^E, then copying with ⌘C, moving to new line, alligning cursor, and finally pasting with ⌘V;

or (2): ^A (set cursor to line begining), ^SPACE (set mark), ^E (set cursor to line ending), ⇧^W (Select to Mark; customized), copy, new line, etc.

As Frank Schröder (in the related question) put it:

The whole point is NOT to use the Cmd-C/Cmd-V shortcuts.

Answer 1

1. Go to this folder which contains dark side of the force:

   • Xcode 4.2 or prior: /Developer/Library/PrivateFrameworks/IDEKit.framework/Resources
   • Xcode 4.3 or later: /Applications/Xcode.app/Contents/Frameworks/IDEKit.framework/Resources.

2. Open IDETextKeyBindingSet.plist.

3. Add a new dictionary and a new command item as the screenshot below (name them what you want):
   

   That’s: selectLine:, copy:, moveToEndOfLine:, insertNewline:, paste:, deleteBackward:

4. Restart Xcode and go to Preferences – Key Bindings, search for your command.

5. Set a key combination for the command:
   

6. Finally unleashed the power of key bindings on Xcode… Enjoy it!