Can I pass a reference to an array element?

[Tukcedo]

LiveCoders,

I read somewhere that you can't pass a reference to an array element, just the array itself. Is this still the case?

What I would like to do is assemble and position on screen a few images that the user selects. Each time the user chooses the "Select Image" button I increase a value and then call the function. It works fine for a situation where I want only a single image, but not when I use the array element.

This one is what I'd like but doesn't work:

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local pImageArray
local pImageCount

on doSomething
add 1 to pImageCount
call "selectImage album,pImageArray[pImageCount],100,35,480" on card "Library" # does NOT work: the 2nd value passed is empty
end doSomething

Elsewhere in the app this works:

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local pImage

on doSomething
call "selectImage album,pImage,100,35,480" on card "Library" # works fine: the 2nd value passed is "pImage"
end doSomething

[FourthWorld]

It works here, but initially did not appear to, because I was incrementing pImageCount beyond the number of elements in pImageArray. You may want to double-check the array to ensure you're obtaining a value for which there is a key.

It should work, because here you're passing by value rather than by reference (no "@"). In a recent version they also added the ability to pass array elements by reference, but that shouldn't affect the code you have here.

[Tukcedo]

Considering we're always dealing with associative arrays in LC (as far as I understand it) and so the elements are created as we go along, I've made sure (I'm putting an "answer" in the code) that pImageCount is actually "1" when we start. Therefore I believe that pImageArray[1] is a valid reference.

Perhaps I should try the '@' method then ...

[bn]

Hi Tukcedo,

try this in a button on card 1 of a stack

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on mouseUp
   put "2,1,3" into tLIstArray
   split tListArray by comma
   put any line of the keys of tListArray into tKey
   put tListArray[tKey] into tHowOften
   call "selectSomething tListArray[tHowOften]" of card "library"
end mouseUp

put this code into the card script of another card called "library"

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on selectSomething pItem
   beep pItem
end selectSomething

this works for me an I think it is a good approximation to your original code.

this has nothing to do with associative arrays or referenced arrays (@), trust Richard.

Kind regards
Bernd

[Tukcedo]

Interesting thought Bernd, but I don't quite understand what it does

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on mouseUp
   put "2,1,3" into tLIstArray
   split tListArray by comma                                          # so now we have tListArray[2], tListArray[1] and tListArray[3]
   put any line of the keys of tListArray into tKey            # looks like we're back at 2, 1, 3 again, the keys of tListArray, right?
   put tListArray[tKey] into tHowOften                           # shouldn't we put this in a loop?
   call "selectSomething tListArray[tHowOften]" of card "library"
end mouseUp

put this code into the card script of another card called "library"

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on selectSomething pItem                                   # pItem will be 2, 1, 3 when called in the order above, right?
   beep pItem
end selectSomething

[bn]

Hi Tukcedo,

split tListArray by comma # so now we have tListArray[2], tListArray[1] and tListArray[3]

no we have an array with the key -> value pairs of

1 -> 2
2 -> 1
3 -> 3

put any line of the keys of tListArray into tKey

this puts a random key of tListArray into tKey

put tListArray[tKey] into tHowOften

puts the value of the random key of tListArray into tHowOften, tHowOften is used as a key in tListArray[tHowOften] in the call line.

this all is to get some randomness into the array key (probably too complicated, just wanted to show that a variable used as a key of an array in a call statement works.


change in the example stack you made the code of the button of card 1 to

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local sListArray

on mouseUp
   put "2,1,3" into sListArray
   split sListArray by comma
   put any line of the keys of sListArray into tKey
   doCall tKey
end mouseUp

on doCall pKey
   put sListArray[pKey] into tHowOften
   call "selectSomething sListArray[tHowOften]" of card "library"
end doCall

and the script of card "library" to

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on selectSomething pItem
   put "" into field "fRes" of card "main"
   beep pItem
   put "you made me beep " & pItem & " times" & cr &  the milliseconds into field "fRes" of card "main"
end selectSomething

you would have to add a field "fRes" to card 1. I think this code is a bit cleaner and also adds the the array in a script local variable.

All this makes me believe that something else is going on in your case. It is not the array-thing.

Kind regards
Bernd

[Tukcedo]

Excellent, I'll try a little PoC tomorrow. Thx for the help!

[Tukcedo]

UPDATE:

After doing some tests it turned out that the mobilePickPhoto that I was using deeper down actually just wants a file name, rather than a variable. So after setting the array item to a name, it worked like a dream ...

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put "Image_" & pImageCount into pImageArray[pImageCount]