Lua about "." The difference between the usage and the ":" Sign

"." Use of:

    Tsprite = {        0,        0,    }     function  Tsprite.setposition (M, x, y)         = x;         = y    end    local who = tsprite
Tsprite = Nil    12)    print(who.x, WHO.Y)

--Output: 1 2

Usage of ":"

    Tsprite = {        0,        0,    }     function  Tsprite:setposition (x, y)-different         = x;         = y    end    local who = tsprite
Tsprite = nil    who:setposition (12)--only this differs     from print(who.x , WHO.Y)

--Output: 1 2

Do you see the difference? Yes, there's a missing caller parameter.

    Who.setposition (who, 1, 2)

    Who:setposition (1, 2)

Use the ":" equivalent to automatically enter the caller's parameter, either: the front table. ---Self is the default parameter hidden in LUA--the caller
and ":" This usage is mostly used in Lua's "class" usage, because after using ":", you can think of Tsprite as a class, and SetPosition () is Tsprite member method, but he needs to be in the outside definition of the class.

Lua about "." The difference between the usage and the ":" Sign