Corona Sdk (lua) hide/show slots and change attachment

Two basic questions about spine in lua at runtime, please:

1- How to hide/show a slot with lua?.

2- How to change an image for other one inside a slot? , example:

(o) Slot

    X Image1

    - Image2

:think:

I answer myself:

local mySlot=skeleton:findSlot("hair")
mySlot.a=0

skeleton:setAttachment("hair", "hair_2");