Swift, save string in property list

I've a plist file named as "data.plist" like this:

I have six arrays, and I also have 6 buttons and a text field. I would like to save the string in the text field to the correct array when I press the right button.

There are many approaches, here is one:

• Name the keys for the arrays in the plist dictionary livello_0 - livello_5.
• Assign tags 0 - 5 to the buttons (indexes are zero-based).
• When a button is pressed, get the tag (let tag = sender.tag) and get the array with let array = data["livello_\(tag)"].
• Update / write the value.
• If it is a Swift collection type, assign the array back to the dictionary (value semantics).