http://stackoverflow.com/questions/551383/xcode-duplicate-delete-line

http://stackoverflow.com/questions/10266170/xcode-4-duplicate-line

适用于最新的Xcode 4.5.1

打开/Applications/Xcode.app/Contents/Frameworks/IDEKit.framework/Resources/IDETextKeyBindingSet.plist，

在Deletions下面增加：Delete Current Line，值为：

deleteToBeginningOfLine:, moveToEndOfLine:, deleteToBeginningOfLine:, deleteBackward:, moveDown:, moveToBeginningOfLine:

在Insertions and Indentations下面增加：Duplicate Current Line，值为：

selectLine:, copy:, moveToEndOfLine:, insertNewline:, paste:, deleteBackward:

然后重启Xcode，打开设置，Key Bindings，找到“Delete Current Line”和”Duplicate Current Line”这两项，设置为自己想要的快捷键。

原文地址：http://blog.csdn.net/meegomeego/article/details/12971089