String compatibility error, attempt to index a nil value

Question

I am using Gideros and getting this error:

    main.lua:47: attempt to index a nil value
stack traceback:
    main.lua:47: in function 'func'
    [string "compatibility.lua"]:36: in function <[string "compatibility.lua"]:35>

I have this piece of code and as soon as the text is displayed, it gives me the above mentioned error:How can I fix this?

function onEnter()
    function youLoose()
    local font2 = TTFont.new("billo.ttf", 20, "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
    LooserText = TextField.new(font2, "You Loose   , Try AGAIN?")
    LooserText:setPosition(100, 100)
    stage:addChild(LooserText)
    Timer = Timer.delayedCall(1000, removing)
    end --line 36
   end   
    function removing()
    LooserText:getParent():removeChild(LooserText)  --line 47
    end

That's not the full error message, only the location. What is the error message? — Colonel Thirty Two, May 14 '14 at 00:30
Also you "lose" a game/race and something is "loose" when it doesn't fit well. Also you probably don't want to overwrite `Timer` like that assuming the returned value from that call is not the `Timer` module and that `Timer` is a module and not an instance of a timer. — Etan Reisner, May 14 '14 at 01:36
need to know what is line 32 in your code; need full message and mark line where error occurs — Oliver, May 14 '14 at 13:36
@EtanReisner : Yes, that's right,I am getting an error there, but what shall I have there instead? — systemdebt, May 14 '14 at 16:31

score 1 · Answer 1 · answered May 14 '14 at 16:59

1

The index nil error means that on that line you are probably getting nil as a return value from LooserText:getParent().

Why you would be getting nil for that I can't tell you other than presumably because it doesn't have one.

answered May 14 '14 at 16:59

Etan Reisner

77,877
8
106
148

I suppose,It should work with stage:removeChild(LooserText) but apparently it didn't.If I added the text to stage, then I certainly should be able to remove it from there and in that case, it says it should be a child of stage if I want to be able to remove it from there, any idea? – systemdebt May 14 '14 at 17:02
What didn't work about `stage:removeChild(LooserText)`? I don't know anything about gideros but I would also assume that should work. – Etan Reisner May 14 '14 at 17:05
Apparently, it did not. The error message said that LooserText should be a child of stage, If I added it to stage, it definitely is a child of that did not work at all. – systemdebt May 14 '14 at 17:23
Are you doing anything else with `LooserText` somewhere else in the code? – Etan Reisner May 14 '14 at 18:07
If you check the number of children the stage has before you call `stage:addChild(LooserText)` and again after that does it change? – Etan Reisner May 14 '14 at 18:48
Since the text was rendered on the screen so there is no doubt, it definitely was added to stage, other wise text won't be rendered – systemdebt May 14 '14 at 19:09
That doesn't answer the question, as such. We are trying to figure out why removing it would not work so we need to check assumptions like this one. – Etan Reisner May 14 '14 at 19:32

score 1 · Answer 2 · answered May 15 '14 at 01:28

The documentation indicates that there is no error condition for Stage.addChild except that the object added must be a Sprite. TextField inherits Sprite so there is no apparent reason for you to get this error. However, you should not re-assign the return value of delayedCall to a global variable of same name as the Timer class, this could affect other parts of the application. Since you don't use the returned Timer instance, I have removed the assignment. Also, if the stage:addChild succeeded then the removing can use stage. One thing that is strange is that your onEnter just defines youLose() but does not call it or return it, is this part of code you ommitted? In any case, you need to add some sanity checks to verify that what you think is happening is really happening w/r/t child add/remove:

function onEnter()
    function youLoose()
        local font2 = TTFont.new("billo.ttf", 20,   "1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
        LoserText = TextField.new(font2, "You Lose   , Try AGAIN?")
        LoserText:setPosition(100, 100)
        print('Stage num children:' .. stage:getNumChildren())
        stage:addChild(LoserText)
        print('Stage num children:' .. stage:getNumChildren())
        print('LoserText is stage child #' .. stage:getChildIndex(LoserText))
        Timer.delayedCall(1000, removing)
     end 
end

function removing()
    print('Stage num children:' .. stage:getNumChildren())
    print('LoserText is stage child #' .. stage:getChildIndex(LoserText))
    stage:removeChild(LoserText)
    print('Stage num children:' .. stage:getNumChildren())
end

String compatibility error, attempt to index a nil value

2 Answers2