Installation
What You Need Before You Can Begin
Before you can begin creating iOS applications with the ArcGIS API for iOS, you will need a few things.
Machine Requirements
Development using the ArcGIS API for iOS requires an Intel-based Macintosh running Snow Leopard (OS X 10.6.2 or higher).
If your Mac is not running a supported OS X version, you will need to upgrade. Please refer to the Mac OS X Technical Specification to determine whether or not your machine supports upgrading.
Device Requirements
Applications built with ArcGIS API for iOS can be run on iPhone 3G, iPhone 3GS, iPhone 4, iPod touch, and iPad devices. These devices must be running iOS version 3.1.2 or higher (iOS 4 is supported where available). We strongly recommend that you test your applications on actual devices to ensure that they work as expected and perform well. Testing on the simulator alone does not provide a good measure of how the application will perform on the physical device.
Apple's iOS SDK
If you are not one already, you will need to become a registered Apple developer. Apple requires this step before you're allowed to download the iOS SDK. To sign up, navigate to the registration page and enroll.
Once registered, you can then go to the iOS Dev Center, log in and download the iOS SDK onto your machine. Note that XCode (the developer toolset for iOS application development) is included in the download as well so you do not need to purchase any developer tools to build iOS applications - that is included in the enrollment fee.
ArcGIS API for iOS is compiled using iOS SDK 4.0.2. You will need to use either iOS SDK 4 (or higher) or iOS SDK 3.2 to develop your applications. Note, you can still run your applications on older devices by configuring your Xcode project's iPhone OS Deployment Target build setting. Be sure to add runtime checks where appropriate to ensure that you use only those iOS features available on the target platform/device. If the features are not available, your application should follow an alternate code path otherwise it might crash on the device.
If you encounter build problems while using iOS SDK 4.1 as described in this thread, you may need to add -D__IPHONE_OS_VERSION_MIN_REQUIRED=030102 to the Other C Flags section of your project's build settings.
Installing the ArcGIS API for iOS
Once you have installed Apple's iOS SDK, you will need to download and install the ArcGIS API for iOS. This can be found at the ArcGIS API for iOS Resource Center.
Stepping through the install wizard installs the API by default under ${HOME}/Library/SDKs/ArcGIS.
The header files are installed under ${HOME}/Library/SDKs/ArcGIS/iOS.sdk/user/local/include
The static library is installed under ${HOME}/Library/SDKs/ArcGIS/iOS.sdk/user/local/lib
And the API resources (images, etc) are installed as a bundle under ${HOME}/Library/SDKs/ArcGIS/iOS.sdk/user/local/resources