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The iOS software development kit (SDK) includes the popular SQLite library, a lightweight yet powerful relational database engine that is easily embedded into an application. In this course, Bill Weinman teaches you how to build an RSS reader for iOS devices, integrating XML data and a streamlined interface. He explains how to use the SQLite database, display information in a table view, code view controllers, and create a preferences pane for your app. The resulting application is optimized for all iPhone and iPad displays.
On the main view of the BWRSS app you will see a button with a plus sign. This is for adding a new feed. When you press on the Add Feed button, a modal view appears with the form for adding the feed. This is a common visual model for an add item action, so it will be familiar to the user. It's a modal view because it's temporarily displayed on top of another view, and it must be dealt with before returning to the parent view. A modal view is typically used to present an edit page or additional details of a model object.
Take care to always include clear and prominent completion and cancel buttons. In this case, the completion button is labeled Add. A modal view is a very different kind of animal. When you're using a modal view, you'll want to keep a few things in mind. Never display an alert or any other modal object from a modal view. The danger is that the modal view may be dismissed before the alert, and this would leave the alert orphaned and cause your app to crash. Never communicate directly with another view object, including your parent view.
You may be tempted to pass a view object pointer to your modal view to make it easy to send messages back and forth. Again, it's just too easy to orphan your pointer, leaving a nasty memory leak or worse. The easy thing to do is to create a delegate protocol and communicate with that. I know this sounds complicated, but it's actually very easy to do in Objective-C, and I will show you how in this chapter. A modal view is a powerful tool and like any powerful tool, it must be used with care. Visually, it's a strong indication to the user that it is necessary to enter some information or take some action immediately.
You just need to make sure that there is a very clear path out of the modality, and that it's easy to get back to the normal workflow.
Find answers to the most frequently asked questions about iOS SDK and SQLite: Building Data-Driven Apps .
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A: The RSSDB library had to be updated to work around a bug in the iOS 7 SDK.
There is a bug in the iOS 7 SDK that prevents the BWDB fast enumeration implementation from working on a device. The symptom is code that runs fine on the emulator, but not on a device. iOS devices use an ARM processor, while the emulator runs on your Mac's Intel processor. This points to the LLVM ARM code generator as the source of the bug. Because the bug appears to be in the LLVM compiler, it may be some time before it is fixed.
As a workaround we have changed the getFeedIDs and getItemIDs methods in the RSSDB library so they don't use Objective C fast enumeration.
Please note that this same bug also affects some of the BWDB testbed code in Chapter 2. The result is that it will run on the emulator but not on a device.
"Used type va_list (aka_builtin_va_list) where arithmetic or pointer type is required"
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