先执行命令修改权限

sudo chmod 666 /Applications/Xcode.app/Contents/Frameworks/IDEKit.framework/Resources/IDETextKeyBindingSet.plist

sudo chmod 777 /Applications/Xcode.app/Contents/Frameworks/IDEKit.framework/Resources/

修改plist

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

1在Deletions下面增加：
“Delete Current Line”
String类型
值：deleteToBeginningOfLine:, moveToEndOfLine:, deleteToBeginningOfLine:, deleteBackward:, moveDown:, moveToBeginningOfLine:

在Insertions and Indentations下面增加：Duplicate Current Line，String类型 值为：
selectLine:, copy:, moveToEndOfLine:, insertNewline:, paste:, deleteToBeginningOfLine:, deleteBackward:

设置快捷键：Xcode > Preferences > KeyBindings 找到对应新增的快捷item,然后添加快捷键。保存重启xcode即可。

目前复制与删除快捷可以用，但是复制的时候，插入的位置是复制当前行后的第二行。奇怪了。