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The online example of tween() can not run with the parameter "fillColor = color(255)"

edited October 2014 in Bugs Posts: 99

When I try to run the example, I found that it can not run.

The error info is:

Error: [string "-- tween.lua ..."]: 133: attempt to perform arithmetic on local 'v' (a userdata value)

I tried the example on my two devices iPad with iOS8, mini with iOS7, the same problem.

If anyone found it before?

Here is the test code, copy from online help

-- TestProj

-- Use this function to perform your initial setup
function setup()
    print("Hello World!")

    box = { x = 10, y = 10, width = 20, height = 20,fillColor = color(255) }

    -- tween(1, box, {x = 100, y = 100})

    tween(1, box,   {fillColor = color(255,0,0)})


-- This function gets called once every frame
function draw()
    -- This sets a dark background color 
    background(40, 40, 50)

    -- This sets the line thickness

    -- Do your drawing here



  • Only numbers can be tweened, not 'userdata values' such as colors. Therefore, you would have to tween the red, green, blue, and alpha values separately (in the target table).

  • Posts: 371

    It is possible, you just have to tweak the metadata values for the color class. Just copy and paste this code into your project:

    mt = getmetatable(color())
    mt.__add = function (c1, c2)
        return color(c1.r + c2.r, c1.g + c2.g, c1.b + c2.b, c1.a + c2.a)
    mt.__sub = function (c1, c2)
        return color(c1.r - c2.r, c1.g - c2.g, c1.b - c2.b, c1.a - c2.a)
    mt.__mul = function (c, s)
        if type(c) ~= "userdata" then
            c, s = s, c
        return color(c.r * s, c.g * s, c.b * s, c.a * s)
    mt.__div = function (c, s)
        if type(c) ~= "userdata" then
            c, s = s, c
        return color(c.r / s, c.g / s, c.b / s, c.a / s)
  • edited October 2014 Posts: 99


    @Saturn031000 If the example code can not run, I think the online example should be modified, otherwise, beginners like me are very easy to be confused with the example. @Simeon

    @Jordan When I add the 'mt' code , it is ok. It seems that you have showed a new way to change the Codea`s behavior from inside! Very good!

  • dave1707dave1707 Mod
    Posts: 7,554

    @binaryblues Here your code modified a little. Is this what you were trying to do.

    -- TestProj function setup() box = { x = 10, y = 10, width = 20, height = 20,fill(255,0,0) } tween(5, box, {x = 400, y = 400}) end function draw() background(40, 40, 50) rect(box.x,box.y,box.width,box.height) end
  • @dave1707 I am reading the tutorial "Codae for beginners" written by @Ignatz ,

    and try all examples in it, my code is from here:


    The tutorial is a good ebook, help me to understand the function tween() clearly. When I read the online help, the code is too simple to run; when I read the example project, it is so complex(mess the class,table together) and it is not good for beginners to understand the usage of tween().

  • dave1707dave1707 Mod
    Posts: 7,554

    @binaryblues Why that example is written like that will have to be answered by @Ignatz. I took your code above and tried to run it and got the same error. The fill command is used for color, so that's what I tried and it worked.

  • IgnatzIgnatz Mod
    Posts: 5,396

    I just copied the online help, will have to edit that

  • @dave1707 What my meaning is that the online help document code has some errors, and it maybe confuse the beginners, so we should correct it. It is a manual bug.

    @Ignatz thanks for your tutorial! It is nice for beginners.

  • IgnatzIgnatz Mod
    Posts: 5,396

    @binaryblues - thank you for the kind words

  • edited October 2014 Posts: 216

    Another option you could use would be vec4's. It's works good and seems easier than editing metadata.

  • SimeonSimeon Admin Mod
    Posts: 4,932

    Support for using color objects in tween() will be available in the next version.

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