Archive for the ‘Technical’ Category
The Xcode Expressions Window
Thursday, July 22nd, 2010
Last week I asked folks on twitter whether they’d like a tutorial on using the Expressions window in Xcode for debugging. Many people replied that they’d never heard of it, so I decided it was probably worth doing.
I’ve just added the tutorial over on the Tutorials page: Using the Expressions Window
The Expressions window is a powerful debugging tool available in Xcode that allows you to evaluate expressions or even call methods on your objects while stopped at a breakpoint in your code. Check out the tutorial for an introduction to some of the cool things you can do with it.
You’ll also noticed that I added a new page in the sidebar for Essays. I’ll group blog posts related to art and video games under that page. Right now there’s just one from January of this year, but I’ve been working on a new one that I hope to have up soon.
Owen
Custom App URLs
Monday, June 28th, 2010
Last week on twitter @mysterycoconut posted a blog post about his cool web-based level editor and that kicked off a discussion about us bloggers wanting to post more regularly to our blogs. With that, #iDevBlogADay was born and I’m happy to be a part of it. Each day of the week there are two iPhone developers blogging about whatever they want. The rules are simple: post a blog article on your day, or you’re out. I’ve been assigned to Mondays, so this is my first post because of iDevBlogADay. You can see a full list of participants in the right sidebar of the site. You can subscribe to an aggregate feed of all posts here: Group RSS Feed.
Have you ever thought “I wish there was a way to click a link in an email and launch my app…” Well there is, through the magic of custom app URLs. The basic idea is this: register a custom URL protocol with the iPhone, and if someone clicks a link with that protocol on that device, it will launch your app. But wait, there’s more: because it’s a URL, you can pass parameters into the app on launch. If you’re a C programmer, this is like being able to pass command line parameters into the application as an argv list.
I first started looking into this in detail while working on LandFormer. In LandFormer, I wanted a nice and simple way for users to share levels they had created without having to use a 3rd party social gaming system or Facebook. I started looking into custom URLs and discovered it could do everything I wanted. Using these URLs, I can encode a level’s data as a URL, embed it in an email, and let the user send an email to their friend. When the friend opens the email on their iPhone and clicks the link, LandFormer is launched, it parses the URL, and loads the level. It’s simple, elegant, and it’s easy to set up once you know where to look. So let’s do that now.
Define a Protocol
The first thing you need to do is decide on a custom URL protocol for your app. Choose something that other apps aren’t going to use. Don’t pick http, because that’s already taken. Pick something related to your app name, or website URL (e.g. “myAwesomeApp://”).
Once you’ve picked your custom protocol, you need to tell your app to register it with the phone. You do this through the app’s Info.plist file. Open the plist file in Xcode. Add a new row of type “URL types”. When created it will contain one item by default, “Item 0″. Expand Item 0 and you’ll see one element inside called “URL identifier”. This is an identifier that must be unique. Use the reverse domain naming system that Apple recommends (e.g. “com.mycompany.myawesomeapp”). Now add a new item to the array under the URL identifier row. Set the new item to “URL Schemes”. This creates an array with one item in it, “Item 0″. Set Item 0’s value to be your custom URL protocol (e.g. “myAwesomeApp”). Save the plist.
Great! Now you’ve told the iPhone that when a URL starts with “myAwesomeApp://” that it should launch your app. If that’s all you want to do, you’re done! Go have a soda. However, this method allows us a lot more power over how we launch the app, so let’s see what we can do with it.
Handling a Launch URL
When your app is launched with a custom URL, you have access to that string when the app launches. This means that you can take different launch actions based on what’s in that string. Let’s take a look at how to do that.
Right now in your app you probably have a function in your app delegate that looks like this:
- (void)applicationDidFinishLaunching:(UIApplication *) application
{
// Do some launch stuff
}
That’s the application where you’d set up your connections between your window and your root viewcontroller, etc. However, in order to handle that custom URL, we need to handle things a bit differently. There are two options.
1) Leave your code in applicationDidFinishLaunching: and handle the URL in a later call to application:handleOpenURL:
2) Replace your applicationDidFinishLaunching: method with application:didFinishLaunchingWithOptions:
[EDIT (2010-07-30): As Jerrod pointed out in the comments below, if you want your app to handle URLs when your app is in the background in iOS 4, you must use handleOpenURL. When an app regains focus because the user clicked a custom URL, you will not get a call to application:didFinishLaunchingWithOptions, but you will get a call to application:handleOpenURL.]
I’m going to talk about the 2nd method, since I’m assuming we’re in a situation where we want to set up a different initialization sequence based on the URL passed in. So lets replace our applicationDidFinishLaunching: method with this:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Do our launch stuff here now
}
Notice that we now get an extra parameter passed to us in the form of an NSDictionary of launch options. One of these options is our launch URL, so let’s fish that out:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Get our launch URL
if (launchOptions != nil)
{
// Launch dictionary has data
NSURL* launchURL = [launchOptions objectForKey: UIApplicationLaunchOptionsURLKey];
// Get the part of the URL after the ://
NSString* queryString = [launchURL query];
// Escape the string
NSString* escapedQuery = [queryString stringByReplacingPercentEscapesUsingEncoding: NSUTF8StringEncoding];
// Parse the URL string
...
}
// Do our launch stuff here now
}
So all I’ve done there is grab the URL out of the dictionary. The call to [launchURL query] grabs the part of the URL after the ://. So if the URL was:
myAwesomeApp://?myString=test&myInt=0
then calling -query on the URL returns:
myString=test&myInt=0
The call to -stringByReplacingPercentEscapesUsingEncoding will convert all the URL-safe characters (like %20 for a ’space’ character) back into the proper ascii char (or in this case, UTF8 char).
Parsing the data can then be done with your favourite parsing method (in LandFormer I used NSScanner to parse each element). You could also parse the data and store the vars into an NSMutableDictionary so that you could then do key-based lookups on the data.
After that, it’s up to you how you want to use that data. You can make decisions about how you want the game to load.
The LandFormer Example
To put this into perspective, the LandFormer URL looks like this for a created level that someone is mailing to a friend:
landformer://?title=Over%20The%20Hills%20And%20Mountain&moves=13
&level=3343333333141222311002000
&check=13F24CFE848198A8BDB8196494904B16
So you can see that the URL is made up of 4 variables: title, moves, level, and check. The check is a checksum done on the data to make sure that the URL hasn’t been messed around with (so as to stop players from sending their friends impossible levels). The rest of the data is self-explanatory.
When the game loads, if a URL is found, it parses the data to get all the information it needs to load that level, then lets the user start playing the level. So if the user has loaded the game directly from clicking on a link, they aren’t taken to the Main Menu, they’re taken straight into the game so they can play their friend’s level.
Cool Side-Effects
One of the really cool side-effects of this method for sharing levels is that these links work from inside a web browser, email, or even a twitter client. So if someone creates a level, sure, they can send it to a friend via email inside the game. But, they can also collect level URLs they’ve created and create their own level packs by posting the links to their website. Then anyone can click those links to play their levels. They can also share the links on twitter, and anyone browsing using an iPhone twitter client (who also has the game), can just click the link to download the level. The possibilities are endless!
Another cool potential use for this would be to allow you to pass data between two of your own apps. Say you make a new game. You could register a custom URL protocol for it, then add a special link inside your old game that allows users who have that game to click it to unlock something in the new game.
A Word on Error Handling
So far everything I’ve mentioned is all of the “look how awesome this is” variety. However, it’s important to mention code security. Any time you allow the user access to data that affects your game, you need to be careful. When parsing the URL coming into your app, make sure you’re handling failure cases well. You don’t want your app to crash if someone starts messing around with the URL manually. You don’t want to give them access to your app’s memory. Be careful with how you parse that data, make your error checking and handling robust, and you should be fine.
Now go have fun!
Owen
My First GDC
Friday, March 19th, 2010
I returned home from the Game Developers Conference (GDC) nearly a week ago, but I feel like it has taken me this long to be able to recover from the late nights, the jetlag, the cold I caught, and put things into perspective. I thought I’d share a summary of my experience there, for those who are thinking of maybe going next year.
Executive Summary: SO AWESOME!!!
GDC is held every year in San Francisco. I’ve been in the games industry for over 6 years now, but this was my first time at the conference, so I wasn’t really sure what to expect. I managed to get an All Access Pass to the conference, so I was there for the summits and tutorials, as well as the main conference.
Let me back up a little and talk about my reasoning for going, as that will help you understand why the conference was so valuable to me. At the beginning of the year I started thinking about what conferences I wanted to attend. 360iDev was a must-attend for me, so I booked that first. However, I was torn between attending WWDC (Apple’s big annual conference) or GDC. I attended WWDC last year and it was great. But this year I felt like what I really needed was general game design inspiration, and less Apple-specific technical inspiration. With that in mind, I chose GDC. My goal for the conference was to focus mainly on game design sessions and take in a few technical and business sessions.
So, I arrived in San Francisco Monday, March 8th, the day before the Summits started. I managed to meet up with a bunch of iPhone devs I know from Toronto, other conferences, or Twitter. We had a few beers and tried to adjust to west coast time. It was a good way to ease myself into the week.
Tuesday and Wednesday were the Summit & Tutorial days at GDC. There were two summits I was interested in: the iPhone Summit, and the Independent Games Summit (IGS). I think I spent about 60% of my time at the IGS and about 40% at the iPhone Summit. I saw some great technical iPhone talks by Noel Llopis from SnappyTouch and Phil Hassey from Galcon. I also saw some great IGS talks that ranged in topic from managing an independent game studio’s creative process, to how to better design indie games. I saw a session by Ron Carmel from 2D Boy, several awesome sessions by the people at thatgamecompany (Flower is one of my favourite games), and a terrific session by Randy Smith from Tiger Style (among so many others!). By the end of the Summits, my head was already spinning with inspiration. The IGS design talks in particular were extremely motivating for me. Getting a chance to meet and hear amazing indie game designers/developers talk about their processes was fantastic. It started me thinking about a lot of things as they relate to my own processes. More on that later…
A tiny segment of the massive GDC Expo
The IGF Awards
Thursday through Saturday were the main conference, expo, and Independent Games Festival Awards. I sat in session after amazing session listening to industry leaders in game design, technical development, and business talk about their processes. I saw Peter Molyneux talk, Sid Meier talk, and even Will Wright talk. I saw a moving and inspirational talk by Brenda Brathwaite on her exploration into board games with serious themes. I saw a head-ache inducing (in a good way!) talk on PixelJunk Shooter’s real-time fluid dynamics system that made me really miss doing PS3 SPU programming. I saw an in-depth and honest look a the successes and problems encountered by Naughty Dog’s attempts to create an active cinematic experience for Uncharted 2. I was blown away by the quality of the content, and I was left reeling by how the talks started forcing me to think about the direction I want to take with my own games.
There were huge crowds in the halls between sessions!
But of course, the sessions are only part of GDC. The other part comes from meetings and parties. I was able to set up a few meetings with iPhone press to show them my new game. That was really great to be able to demo the game in person. I think it was extremely valuable. Then each night there were countless parties happening. Each party was a great chance to meet people in person who I’ve only communicated with on twitter or via email. It was a chance to discuss iPhone development with other people going through the same thing as me. It was a chance to discuss game design in general with other game designers and developers. It was a chance to have fun with people who share in the same daily challenges that I do.
Will Wright giving his presentation!
For me, I got out of GDC exactly what I wanted: design inspiration, new friends, new business connections and a wealth of knowledge. But perhaps most importantly, GDC helped me to put me back on track with where I want to take my games. When I decided to go indie in 2008, it was because I wanted to make the games that I was compelled to make. What I’ve noticed is that I’ve been making more and more design decisions lately based on what I think will sell well. This isn’t how I want to make games. I want to make the games that I have to make, not that I think I should make because I think it might make some money, even though the idea doesn’t excite me. Granted, I would love to be able to make the games that I feel compelled to make and have them also become a financial success. And obviously I can’t ignore the fact that I’m running a business. But GDC helped to remind me of what I want my priorities to be, and that, to me, is the most important part of having gone.
Owen
GDC, 360iDev, and More
Friday, February 19th, 2010
It has been quite a while since my last post. I would have been posting, but I’ve been doing some contract work, so I haven’t had a lot of my own news to talk about. I’ve also been doing my year-end bookkeeping, and as exciting as that is, I’m not sure anyone wants to read about my adventures in recording business receipts from 2009.
However, over the last few days I’ve been returning to my own projects and getting back into the swing of things. As you might recall, I took part (remotely) in September’s 360iDev Game Jam night and created a prototype for a puzzle game idea I had. I’m happy to report that I’ve been developing that idea further and it’s coming along nicely. The game now looks very different from the screenshot I posted on Touch Arcade, by the way. As for a preliminary look at what the game is becoming, I might have something to show early next week, so keep an eye out for that!
Yesterday I decided to rewrite the rendering part of my engine to take advantage of a bunch of optimizations I had been putting off making. It turns out that the changes I made over the last day reduced my render time by about 40%! That means that I can render nearly double the sprites on the screen without dropping my framerate. This is great news, and I’m looking at porting the changes back into Monkeys in Space at some point to help out with that game’s performance.
In other news, I thought I’d mention that I’ve decided to attend two conferences this spring: the Game Developers Conference (GDC) in March and 360iDev in April. I’m looking forward to both conferences, but I’m especially excited about GDC as I’ve been in the games industry for over 6 years now, but I’ve never gone to GDC! I’m really excited to get a chance to finally go and see what all the fuss is about. I’m also looking forward to attending sessions on game design that are more broad than just iPhone games.
That being said, I’m also happy to be attending 360iDev again. It will be great to see the iPhone developers I speak with every day on twitter in person again. Last year I had a fantastic time at the conference and I expect no less this time. I’ll also be speaking at 360iDev. For my presentation I will attempt to create an iPhone game prototype in 80 minutes based on audience suggestions. While doing that, I’ll be highlighting some of my best practices for rapid prototyping. If you’re attending the conference, I hope you’ll check it out. If you’re not attending the conference, why not? Check out this amazing schedule of speakers. And if you’re thinking about it, go register! 
Owen
-
You are currently browsing the archives for the Technical category.