Sub-classed NSTableView for CMD+A/Select all functionality

SelectAllTable.rb

class SelectAllTable < NSTableView
    attr_accessor :delegator #Connect this to the delegate of your table view

    def keyDown(event) #any time this table is in focus and a key is pressed, this method will be called.
        characters = event.characters
        character = characters.characterAtIndex(0)#let's get the first key that was pressed
        if character == 97 && (event.modifierFlags & NSCommandKeyMask) == NSCommandKeyMask #97 is the "A" key, while the CMD key is a modifier key. Check to see if both were pressed
            @delegator.select_all #call your method that selects all your rows
        else
            super(event) #This isn't what we're looking for, pass it on to super
        end
    end

end

#example select_all method
def select_all
    range = NSMakeRange(0, my_table_array.length) #set the range to include all rows
    indexes = NSIndexSet.alloc.initWithIndexesInRange(range)
    my_table_view.selectRowIndexes(indexes, byExtendingSelection:true) #visually show the indexes
end