iOS/Web Developer's Life in Beta

I’m a big fan of all things Apple, and as you can tell from my past blog posts I’m a big fan of iPhone development. I’ve even dusted off my aging C skills, and have learned to love Objective-C. The one thing I haven’t learned to love, like all other iPhone app developers, is their application release process, and the seemingly arbitrary app store acceptance department.

Don’t get me wrong, I think how Apple fiercely guards the App Store to prevent bad, buggy, or offensive material from getting on there is a great thing. Some of my mother-in-law’s students in the class she works in have iPhones or iPod Touches, and these little 10-year-olds love the little apps I’ve put out. They’re fun, light-hearted, and they get a lot of enjoyment out of these and other apps. It’s reassuring to know that if I install an app, it won’t crash my phone (too badly) or that a child won’t be offended by them (too much).

However, the level of detail they give in their rejections seem both arbitrary and unnecessary. You develop an app and have to throw it over the fence to Apple, after which you wait with no level of detail as to the status, or success, or any sense of progress through whatever queue they have. Finally, you more often than not get a big fat rejection letter that gives you no detail as to why your app didn’t meet their secret criteria.

In my experience so far, this has actually been a virtue. My apps actually did have minor race conditions, or problems on specific platform versions. So, fair enough, I fix my changes and submit them in. But recently, the framework I work with and have been helping develop seems to be under fire from Apple for no apparent reason. And it’s the contradictory nature of their message that is what gets under my skin.

In this long thread on the PhoneGap mailing list, a number of developers writing their applications under PhoneGap have been given rejection letters saying something like:

Upon review of your application, cannot be posted to the
App Store due to the usage of private API. Usage of such non-public
API, as outlined in the iPhone SDK Agreement section 3.3.2 is
prohibited:

” An Application may not itself install or launch other executable
code by any means, including without limitation through use of a plug-
in architecture, calling other frameworks, other APIs or otherwise.
No interpreted code may be downloaded and used in an Application
except for code that is interpreted and run by Apple’s Published APIs
and built-in interpreter(s).

The PhoneGap API implemented in your application is an external
framework.

For those new to PhoneGap, it’s a project that gives you an XCode project directory with Obj-C classes pre-made that allow you to develop iPhone apps in HTML / JavaScript. It wraps up several of the iPhone’s native controls and exposes those capabilities to JavaScript. In this way, an application developer could write their app in a hybrid of native Objective-C code and the iPhone’s own native browser control, the UIWebView.

It seems though that Apple constitues the use of their own controls as a 3rd-party library. Apple’s own developer documentation includes code sample projects, much like PhoneGap’s, intended to get a developer started on using their SDK. Is it incorrect to assume that others can do the same?

Additionally, there are 3rd-party companies such as AdMob, Medialets, and a number of others that provide ads, application tracking, and other resources to iPhone developers. Their code is given to you as pre-compiled libraries, that are most certainly not included on the iPhone when you pull it out of its shrink-wrap. So how is it that all these apps are released to the App Store with these 3rd-party libraries linked in, and an app framework whose source code is freely available and uses officially documented features can’t be?

I decided to put an end to the speculation, and wrote a letter to Apple’s developer support on this matter. I’ll give it a chance to percolate through their support department, and if I don’t hear an answer back via email, I plan to call their support department until I can get an answer.

For future reference, and in the interests of keeping the discussion open, here’s a copy of the letter I sent in to Apple.

From: Michael Nachbaur
Date: May 17, 2009 6:04:28 PM PDT (CA)
To: idp-dts@apple.com
Subject: Library classification clarification

Hello, I’m an iPhone software developer, and one of the core developers of the PhoneGap project. A number of users of PhoneGap – a set of Objective-C classes aimed at leveraging the UIWebView to access iPhone-supported hardware features – have reported that their apps have been rejected from the App Store because they supposedly use a “3rd-Party Library”. I wanted to get some clarification about this, as this is not only untrue, it is completely at odds with the goals of our project.

PhoneGap only uses officially-supported features of the iPhone, as documented within XCode’s iPhone SDK documentation. We even make sure that we don’t even use deprecated features of the iPhone, as we want to ensure 100% compatibility. All the software we use is exposed natively by the iPhone, and is in use in many other apps on the App Store.

So I wanted to get an official clarification from Apple as to why these apps are being rejected, and what, if anything, we as the maintainers and developers of the PhoneGap project can do to rectify the situation. We are trying to empower developers with quality starting-blocks for developing their own applications, much as the Apple sample applications do.

So please, if there’s anything we’re doing wrong, we would more than happily change our code to accommodate Apple’s policies. As far as we can tell, we support Apple’s licenses even better than other apps on the App Store, because we don’t import 3rd-party libraries such as AdMob, Medialets, or any of the other ad and tracking libraries that are obviously featured on almost every app in the App Store. And these are quite plainly 3rd-party libraries, and as such should they not be even more restricted than we are?

As a community, of both software developers and of business-people, we are very anxious to hear back from you, and would like to discuss this with someone at Apple to get an official answer, instead of the conversation being one-sided and filled with speculation.

Thank you for your time, and I look forward to hearing back from someone soon.

What are your thoughts on the matter? Can anyone reading this find some reason why Apple would target PhoneGap?

Update: I got an update on this problem from Steve, one of the app reviewers, over at Apple.

I’ve merged the results of my UIControls branch on github into my master branch. I think my little experiment went well, and I’d love to get feedback from people on how this new API works for you. I still have some great plans for it, but before I get ahead of myself, let me cover what I’ve done:

Changes:
• Refactored the command call API to allow for a richer set of arguments to PhoneGap commands
• Moved some commands around to more appropriate classes (e.g. Alert and Vibrate both moved to Notifications)
• Reorganized the XCode project so commands are clearly separated from PhoneGap infrastructure
• Renamed the Settings.plist PhoneGap config file to PhoneGap.plist, and created a new Settings.plist file that contains custom application-specific configuration.
• Made all PhoneGap commands inherit from a common base-class that auto-loads its own Dictionary of configuration from the main PhoneGap.plist file.
• Added UIControls command class that exposes tab bars and toolbars to JavaScript.
• Updated the demo to show off tabs and toolbars

All that looks like a big change, but almost all of it was infrastructure changes that were necessary to get UIControls to work. Previously, all PhoneGap commands were class method calls, meaning it was very difficult to maintain state between command calls. Now that commands are actually called on an instance of a given command class, it’s easier to maintain state. So when a tab bar is created, multiple calls can be made, each to construct different aspects of the UI. Without all this, the following example would have been much more complicated:

uicontrols.createTabBarItem(“toprated”, “Top Rated”, “tabButton:TopRated”);
uicontrols.createTabBarItem(“recents”, “Recents”, “tabButton:Recents”);
uicontrols.createTabBarItem(“more”, “More”, “tabButton:More”);
uicontrols.showTabBar();
uicontrols.showTabBarItems(“toprated”, “recents”, “history”, “more”);

The changes to the PhoneGap configuration were necessary because now, when a PhoneGapCommand subclass is constructed, it will look in the PhoneGap.plist configuration file to see if there’s anything pertaining to it. So if there’s a key in the dictionary with the same name as the class being constructed, it will use that as a local configuration dictionary influencing just that one class. That way, if you don’t use a feature of PhoneGap, or you have to configure a lot of options for a single type of command, these options won’t be cluttered alongside the standard global PhoneGap settings.

I created Settings.plist because of experiences I had in an application I’ve been creating in order to test my new UIControls branch changes. I found that I wanted to set compile-time options (for instance a “lite_mode” boolean) that influenced the way my app runs, without having to change HTML or JavaScript code every time. So instead what I have is a configuration plist file that is used exclusively in JavaScript for my application. I’ve added the excellent SB-JSON framework in to the PhoneGap project, and use that to pass these settings into the JavaScript application at start-up time. So all you have to do is read Settings.lite_mode, for instance, in order to read properties set in your plist file.

Oh, and finally, I’ve moved the JavaScript documentation to javascript/docs, since they were practically impossible for new users to find in the past. I’ve been working on creating DoxyGen docs of the PhoneGap code for use in XCode’s documentation browser, but I haven’t gotten far enough there to actually check anything in besides comments. I found instructions on how to generate XCode docsets from DoxyGen, but I haven’t gotten it working just yet.

So please, try out my PhoneGap updates and let me know what you think of it. I think the integration of the JSON framework will make things like Contacts much simpler to implement.

Before I go though, I want to give a little “wish list” of features I’m planning on adding in the near future. I’ll get to them whenever I can, since my own app development takes priority of course.

• Toolbar buttons
• Tabbar show/hide animations
• File support (read / write local files)
• Camera and photo library support (POST to a server, save to a local file, etc)
• Native “Flip / Slide” transitions (no more having to mimic them in CSS)
• 3rd party API integration, like AdMob and Medialets (I already have both of these done, but I’m in discussions with both companies to determine if the terms of their license allows me to redistribute it)

I’ve managed to avoid C and C++ programming for most of my career of 15 years. I’ve dabbled, and then I’ve run back to my favourite languages. Besides, as a web developer there hasn’t often been a need for me to delve that deeply into the machine.

Now that I’m developing iPhone applications, that’s all changing. I’m using PhoneGap to develop my apps, but some of it was buggy, and others just didn’t do what I needed to do. I’m integrating the AdMob and Medialets APIs into my application, which means Objective-C programming. After picking my way around, and continuing on the work my friend Scott McWhirter developed, I think I’ve come up with something that not only works well, but helped me to learn and love Objective-C.

Why I started playing in ObjC

Scott had fixed a long-standing bug in PhoneGap which happened when multiple PhoneGap commands were made within the same event loop in JavaScript. After he figured out how it worked, and how to fix it, that showed me just how PhoneGap works. To be honest, this is the first time I really understood how it does what it does.

As I integrated Medialets in, I discovered that it has the capabillity of sending custom tracking events so developers of iPhone applications can not only analyze when and where people are using their application, but what they’re doing while they’re using it. I wanted to use this to see how effective parts of my first application are, so I can learn what to change in the future.

Sadly, since most of my application is written in HTML/JavaScript, there was no direct way I could call out to the Medialets ObjC API directly from my JavaScript events. I couldn’t do copy/paste code any longer, I needed to extend PhoneGap to add my own commands to it.

Why I Refactored PhoneGap

The way PhoneGap commands worked in the past is it would set “document.location” to an address that looks like “gap:command_name”. If any arguments were supplied, they’d be added on the end separated by colons. But since that is a relative path, it would be added on to the end of your application’s filename. So, since HTML files are loaded locally from within the app’s directory on the iPhone, a GAP command would look like:

file:///…MyApp.app/www/gap:command_name

So figuring out if a command is being called involved a lot of hackery around stripping out the gap: portion of the URL. Since this was difficult to deal with, and meant there was a lot of re-used code, not to mention commands couldn’t contain colons, or any characters that could potentially be URL encoded, I refactored GAP commands to be their own absolute paths, like so:

gap://command_name/arg1/arg2/arg3…

When this location is set, a callback within the Objective-C code (called shouldStartLoadWithRequest) checks the address and determines if the request is a real request and should be allowed to continue, or if it should process the command as a GAP command and disallow the link from being loaded.

So these URLs are never loaded outside of the phone. Once PhoneGap sees a gap:// URL, it parses it as a command request and never attempts to fetch the resource. The benefit of this is that the iPhone’s NSURLRequest and URL objects automatically decode the URI parts and escapes any %20-style encodings. It also is a lot simpler to find the name of the command to run, since all it has to do is fetch the URL’s hostname property.

I’ve pushed this to my own fork of PhoneGap up on GitHub if you want to try it yourself. Hopefully these changes get pulled down into the main branch of PhoneGap.

Next Steps

Realizing how easy it is to write Objective-C, I’m planning additional changes in the future. First, I would like to refactor the gap.js JavaScript code to use Joose, a light-weight meta-object class framework. This way, instead of calling out to a separate class like Device.exec to call out to PhoneGap, you could inherit from PhoneGap and create a class-based application that extends it instead.

I would also like to make the commands within PhoneGap pluggable, so one doesn’t have to extend one giant if/else block. Instead, it would be nice to have a pluggable framework where you can add commands by inheriting separate classes. I don’t know enough to do this yet, so unless someone else does something similar, it will have to wait.

Certainly I’ve learned quite a bit, and had a great time doing it! I’m really enjoying PhoneGap and iPhone development, and I’m looking forward to adding more as time goes on.