Xcode - Duplicate Line key binding

duplicate_line_xcode.md

NOTE (2022-07-09): Xcode finally added this functionality in Xcode 14, please see release notes here:

New Features in Xcode 14 Beta 3
When editing code, the Edit > Duplicate menu item and its corresponding keyboard shortcut now duplicate the selected text — or the line that currently contains the insertion point, if no text is selected. (8614499) (FB5618491)

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Xcode line duplicate

Bind keys to duplicate lines in Xcode

1. Close Xcode

2. Open below directory in Finder with Cmnd + Shift + G

/Applications/Xcode.app/Contents/Frameworks/IDEKit.framework/Versions/A/Resources/

3. Open IDETextKeyBindingSet.plist with a text editor.

4. Add this in:

<key>Duplication</key>
<dict>
    <key>Duplicate Current Line</key>
    <string>moveToBeginningOfLine:, deleteToEndOfLine:, yank:, insertNewline:, moveToBeginningOfLine:, yank:</string>
    <key>Duplicate Lines</key>
    <string>selectLine:, copy:, moveToEndOfLine:, insertNewline:, paste:, deleteBackward:</string>
    <key>Delete Line</key>
    <string>selectLine:, deleteBackward:</string>
</dict>

5. Open Xcode and go to Xcode preferences -> Key Bindings -> Text tab -> Scroll till you see Duplication

6. Click on Duplicate Current Line, add a shortcut for it, eg. Cmnd + D (remove any other bindings for this key)

I found that the original sequence can add extra steps to the undo history (CMD + Z). Xcode actually has a native duplicate: command that does the same thing in a single step, keeping the undo history cleaner.

Using duplicate:, I was also able to recreate VS Code’s “Copy Line Up” with just:

selectLine:, duplicate:, moveUp:, moveToEndOfLine:

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<key>Edit menu (ext)</key>
<dict>
    <key>Duplicate current line up</key>
    <string>selectLine:, duplicate:, moveUp:, moveToEndOfLine:</string>
    <key>Duplicate current line down</key>
    <string>selectLine:, duplicate:, moveToEndOfLine:</string>
    <key>Delete Line</key>
    <string>selectLine:, deleteBackward:</string>
</dict>