Three20 Overview
Three20 is conceptually split into four parts. At the center of everything is the Core. Surrounding it are Network, UI, and Style.
Core
Think of core as your swiss-army knife of Objective-C development. You should take some time to familiarize yourself with its features.
With the Three20 Core you can
- generate md5 hashes from NSData objects,
- extend the logging and debug capabilities of Xcode,
- compare two version strings (is 3.0 older than 3.1?),
- create non-retaining NSArrays and NSDictionaries for delegate use,
- strip HTML tags from strings,
- safely add non-empty, non-nil strings to NSDictionaries,
- and format dates in relative time (5 hours ago).
You'll find all of these methods in the Three20 Xcode project in the
Global => Core and Global => Additions => Core groups.
Network
If you're building an app that uses a web-based API, Three20's Network component is going to make your job easier. Three20 supports disk and memory network caching. There is also a layer built upon requests that makes it easy to process the response data.
UI
A growing set of common views and controllers is available within the Three20 UI. The well-known Facebook photo browser/thumbnail viewer is one such controller.
You can easily mimic the Mail app's message composer using TTMessageController. If you want to post messages like the Facebook app, you can use the TTPostController.
There are also view controllers supporting Safari and YouTube.
Three20 includes a powerful table cell/item architecture that comes with a number of extra table cell types in addition to the standard Apple cell types. You can easily create a table controller with controls inline, for example.
If you want to show activity in your app with a little more style than just an activity indicator, you can use one of the Three20 activity labels which provide the indicator + text + progress.
Emulate the iPhone's springboard controller using TTLauncherView.
There's also support for top-oriented tabs.
Style
Three20's Style component is a powerful way to declare and reuse styles. By defining "stylesheets", you can create rounded buttons, drop shadows, gradients, and borders with a few simple declarations. Below are just a few examples of styled elements in Three20.
Is Three20 right for your project?
If you're building a native app that talks to web APIs or accesses images from the web, then Three20 will undoubtedly save you a lot of time. If you're not doing any of that, then you'll probably still find a lot of code within Three20 that you'll find useful. And heck, it's all licensed under the Apache 2.0 license anyway. Pick and choose at your pleasure.
The short of it: yes, it is.
Now that you've gotten a basic idea about what Three20 is, go ahead and play with it.
