Monday, July 28, 2008

Variable Scope Issues

Again, here's a new link to my latest project.
I think it's actually pretty fun, so I hope you try it out.

The only major issue left to tackle is the high score board. When the game ends, you can submit your score to the online scoreboard (I'm currently in first place, go figure.) It was a chance for me to play around with flash's internet communication abilities. It works pretty decently as well, if you ask me. The problem is that, for some reason, the scoreboard only shows up the first time you play it (per page refresh). What that means is that if you press the "Play again" button, play the game, end the game, and submit your score, you won't see the scoreboard. I'm completely scoobied as to why that is. The code to update the scoreboard is as such:

htmltext =;
scoreBox.htmlText = htmltext;

If you're not familiar with flash, trace is a command that outputs things to a special "output" window. Therefore, the variable should be shown on my screen. The problem is that despite the fact that I do get the correct text outputted to me by the trace call, the scoreBox.htmlText doesn't reflect what it was given on anything other than the first time through the game. I had a similar issue (in fact it was the only real major "bug" in the first iteration) with the images from the last scoop being present on replays as well, and that was fixed by making sure that everything was reset properly at the appropriate time.

My guess is that this is a variable scoping issue, partially because that was the issue the first time, and partially because Flash's scoping is about as confusing as watching Memento when you're tripping acid. As far as I can tell, variables instantiated within a frame are scoped globally, unless they're within a loop or function. However, commands, or anything else for that matter, only apply at that specific frame. This kinda makes sense. You might want to use a variable you defined somewhere else in the program, and you don't want all of your code executing at once. The issue here is, when are objects (like the scoreBox) that are defined in the scene, not in the code, created? Are they global? Can I change their values before they're visible? I'm still trying to figure it out, so if anyone has any suggestions, feel free to leave them in the comments.

As far as I can tell, it's only used for debugging, as my experiences with the actual Flash debugger were about as pleasant as shaving with a rusty butter knife.

Wednesday, July 9, 2008

Baby Steps

I think this is probably my first post ever that contains any actual coding in it, and frankly, I'm a little scared. This is such foreign territory for me, I don't know where to start.

So I'll start with a link.

Yes, it is in flash. I feel dirty with this being the first "complete" program I post, but we all have our flaws. I actually haven't paid for Flash CS3, but I'm using the 30-day free trial, and working fast. In terms of development, there are some things I like and some things I really dislike, but I'll get into that later.

If you can't tell by the URL, or the name, it's just a cheesy, quick Space Invaders clone. I programmed it in ActionScript 3, despite never having used it before, in about 3 hours. My main problem so far is that when there is contact between the lasers and their target. The lasers are (obviously) placed dynamically, and in their update method, I tried using the following line to "kill" invaders when they touch.


Which, on top of being horribly hardcoded, throws the following error.

Error #2025: The supplied DisplayObject must be a child of the caller.

I tried everything I could think of, and eventually just decided that it was just a "Flash Thing," until I realized that the lasers were being added like so:


The problem here was that when I was looking at how to dynamically add new objects, the tutorial didn't have their code in a function, it was just on the stage. Therefore, using the keyword this on the frame added for the stage, setting up for a similar removal with this.removeChild(). Apparently, when inside the function, this is not the stage. There was another issue, however.

The Invader still would not be removed via stage.RemoveChild. It continued to throw the "Child of the Caller" error. I intend to dig deeper into this, but not too much, though, since the issue is relatively moot. This is because the Invaders were added to the scene statically, which I found is unlikely to happen in any sort of "normal" game. Things that are dynamically added and removed (just as God intended,) come into and out of the scene without an issue. Not terribly enlightening, but at least it wasn't about the iPhone.