Using a variable to call an image?

What an interesting bug.

Let's simplify the code to what causes the error which is this:

var ageProp = ["seed"];
image(getImage("avatars/primosaur-" + ageProp[0]), 0, 0);

It seemed that the cause of the problem is that getImage() is an asynchronous function. This means that the computer doesn't wait for getImage() to finish running before it runs the next line of code.

It seems this also causes the error

var ageProp = {a: "seed"};
image(getImage("avatars/primosaur-" + ageProp.a), 0, 0);

and this

var ageProp = "seed";
image(getImage("avatars/primosaur-" + ageProp), 0, 0);

It seems the error occurs whenever using a variable in the getImage() command. I thought maybe that the problem was with adding things together in the function. So I made sure that the input to the function was a simple singular string.

function compilePath (path) {
return path;
}
var test = compilePath("avatars/primosaur-" + "seed");
image(getImage(test), 0, 0);

But that actually doesn't work either and neither does doing it more indirectly like this

function compilePath (path) {
return (function () { return path; })();
}
var test = compilePath("avatars/primosaur-" + "seed");
image(getImage(test), 0, 0);

So then I simply removed the addition in the path input

function compilePath (path) {
return path;
}
var test = compilePath("avatars/primosaur-seed");
image(getImage(test), 0, 0);

and guess what it works!

This doesn't work
image(getImage("avatars/primosaur-" + "seed"), 0, 0);

but this does work

image(getImage("avatars/primosaur-seed"), 0, 0);

So what is my conclusion? After doing all my tests it seems that whenever getImage is called, Khan Academy traces the code all the way back to where the string input was created. And if the code is not what they think is a valid string then they throw an error.

That's just my guess. I have no idea why they would do that. I've tried a whole ton of workarounds, but none worked. It seems that the only way you can get this to work is to create a big array of every single possible path and use one of those strings instead of joining strings together to form the path. Which really stinks, but I mean KA doesn't have that much images so it's not that big of a deal.

Actually, SpencerKuan figured it out. KA checks if your program contains a valid path before attempting getImage.

Try the following:

"avatars/aqualine-tree";
image(getImage("avatars/aqualine" + "-tree"), 0, 0, 400, 400);