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Comment by marknutter | Hacker News Reader

I've been thinking about getting into iOS development but I'm on the fence about diving into learning objective-c. I'm a ruby/javascript guy primarily and I think I'd rather go the js route than objective-c, but I want to know what the limitations will be? Anyone have any insight they could share?

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While it is not a pure HTML/JS app (it is a well-designed and engineered hybrid[1]), ivanzhao's Three Degrees shows that someone can ship a well designed app with web expertise.

http://itunes.apple.com/us/app/3-degrees-of-wikipedia/id3998...

[1] http://news.ycombinator.com/item?id=1903732

One obvious limitation is you won't have Cocoa, or the frameworks built on top of it. Want to let the user take a picture using the iPhone's Camera? It only takes 2 lines of code, and it works exactly like the native app. Same goes for showing Google Maps (MapKit), editing contacts (AddressBook), and so on.

Since the book talks about accessing the geolocation facilities of the phone via JavaScript then that should clue you in to that as a kind of lower limit to the limitations. God that's garbled--- I think I mean to say if you can mess with GPS using just JavaScript then you shouldn't have much in the way of limitations. Can't be as good as objective-c and IOS, but this should be for lighter apps anyway.

WebKit has hooks for location services - any website can ask for access to the iPhone's location. It's things like accelerometers, gyros, and camera that are tougher.

It's also next to impossible to make a native feeling application. Scrolling, transitions, animations are all less fluid.

CSS3 transitions are virtually indistinguishable from native animations and transitions, when applicable (i.e. CSS3 obviously can't be used for some things, but is a 1:1 replacement for things like page transitions).

iOS 4.2 exposes accelerometer and gyroscope data to web apps now. http://news.ycombinator.net/item?id=1932107

As for scrolling, a number of JS libraries/frameworks such as SproutCore now implement fake scrollviews using touch events and CSS transforms, transitions and animations. For example: http://touch.sproutcore.com/

As for the cameras, IIRC the Chrome team is proposing APIs for camera access to HTML5.

The main limitation is not technical in nature. The App Store is a marketing force that you get benefit simply by releasing a native app.

Can you name any good HTML/CSS/JS iOS "apps"? Either there aren't many (any?) or people don't know about them (which is basically the same thing)

edit: responses noted, guess I didn't read carefully enough

The book has a chapter on using PhoneGap to automatically create apps that can be submitted to the App Store, so this is not a limitation.

37Signals Chalk is the first that comes to mind. But we're doing a few of these apps where I work, and my HTML5 and CSS3 book shows how to do an offline app with the Web SQL storage API too. This is actually really cool stuff when you think about applications for business. You're not gonna write games with it, but you can make usable interfaces for your apps.

And if you feel the need to be on the app store, grab Titanium, use the Titanium.UI.webview control and point it at your mobile site. We're proably going to do that to make a few of our web apps show up on the stores, because we don't have the resources to develop native Android / IOS versions of the apps we are building. So we'll do Rails apps with HTML5 / CSS3 / JS and jQTouch or jQuery Mobile, and wrap them if people demand appstore access.

Apple have rejected apps in the past that do nothing more than point to a website. A common way to get around that is to implement a feature in native code, e.g. a banking app that points to the website, but has native mapping functionality for finding branches. I am not sure, but I think it's now covered under clause 12.3[1] of the guidelines[2].

1. Apps that are simply web clippings, content aggregators, or a collection of links, may be rejected.

2. https://developer.apple.com/appstore/resources/approval/guid...

You'd likely never even know that an HTML5 app wrapped in PhoneGap or Titanium wasn't native. There are many of those on the app store already. In fact, the subtitle of the book specifically mentions the app store: Making App Store Apps Without Objective-C or Cocoa.

Application that depends on the native browser of the iPhone, such as PhoneGap based application, has severe limitation imposed by Apple on how much memory they can take.

So far, I have downloaded several applications, mostly which I don't really need, to test the experience of PhoneGap based application. I should say, given the limitation, its quite impressive. However, if you are being really picky, its easy to notice if you have say, a list on the application, scrolling the list after the view is opened (even if its the second time), the scrolling isn't so smooth and stutter a bit.

Of course, for normal people (aka non-developers), they may not notice, much else know if it is a PhoneGap application or not.

It's worth noting the response to O'reilly's own Safari To Go iPad app on the Safari Books online blog which was based on PhoneGap. The app has since been pulled from the App Store. See http://safaribooksonline.wordpress.com/2010/11/24/ipad-app-s...

Discounting games, the majority of the apps I've downloaded from the app store could be written with HTML5 and distributed as Titanium or PhoneGap wrapped apps. Some of them probably are and I'm just unaware of it.

For that matter, if I didn't remember I'd used "Add to Home Screen" to get the 37Signals Chalk app on my iPad's list of apps, I probably wouldn't realize it wasn't native.

I second your mention of Titanium. It's a cool JavaScript based SDK for writing mobile apps in general - easily ported to iOS, Android, Blackberry, and mobile web. http://www.appcelerator.com/

You can't upload photos or other files from the web browser in iOS, which is a stupid limitation.

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