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As we ve previously noted, the objects that pull up keyboards are a bit tricky, because you have to explicitly get rid of the keyboard when editing is done. For UITextFields, you can turn the Return key into a Done key to dismiss the keyboard; but for a UITextView, you usually want the user to be able to enter returns, so you must typically create a bar at the top of the page with a Done button. Figure 8.6 shows this layout of items. When the user presses Done, the finishEditing: method C is called, which resigns the first responder, making the keyboard disappear (unless you re not editing, in which case it closes the program). The last two methods are defined in the UITextFieldDelegate protocol. When editing begins on the text field, the program checks to see if the starting text is still there, and if so clears it. When editing ends on the text field, the content is saved to your file. Finally, the keyboardIsActive variable is toggled, to control what the Done button does in each state. As you saw in table 8.4, there are numerous other ways to read files and save them. The methods in listing 8.4 are simple, but they allow you to make good use of your notepad s file. Files are okay to use for saving one-off data, but if you re storing a lot of really large data, we suggest using a database when it s available. And on the iPhone and iPad, a database is always available, as you ll see in chapter 9.
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Figure 8.6 The filesaver application with the keyboard activated on both the iPhone and the iPad
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Data: actions, preferences, and files
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Summary
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In this chapter, we covered a variety of ways that you can import primarily text-based data into your program. User action is one of the most important methods, and one well covered by previous sections. In addition to UITextFields, UITextViews, and UISearchBars, many nontextual interface options are available. Preferences mark the other major way users can influence your program. You can either program them manually or use the System Setting bundle. Ultimately, user input is somewhat limited on the iPhone because of the slow typing speed. If you re dealing with piles of text, you ll more frequently want to pull that data from an existing resource. The iPad doesn t suffer from this issue, because users can type more quickly on the keyboard. Files are the traditional way to access large amounts of data. We ll return to files when we deal with photos and sounds in the later chapters. Databases are frequently an easier way to access data, particularly if the data is well organized, as you ll see in chapter 9. There s only one data-input method that we ve largely ignored: the internet. We consider it so important that we ll cover it in chapter 14. The data-input and -retrieval methods discussed in this chapter and the next will form a foundation for much of the work you do with the iPhone and iPad, because ultimately everything is data. You ll need to retrieve data when you work with images and sounds. Similarly, you may want to save data from your accelerometer, from your Core Location, or when you create a graphic. Keep what you ve learned here in your back pocket as you move on to the rest of the iPhone OS toolbox. We re now ready to discuss more advanced data access techniques, including interfacing with the Address Book and saving persistent data with SQLite.
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This chapter covers
Using SQLite Using the Address Book framework Using Core Data
In the last chapter, we discussed how information can be saved and retrieved on the iPhone and iPad. Those techniques are great for simple data such as user preferences, but what happens when you want to save thousands of records Saving large amounts of information to NSUserDefaults would be awkward and clunky, and serialization is too slow. The solution is to use a relational database. Apple has provided a couple of options for mass storage using relational databases. These options are SQLite and Core Data. We ll look at both as well as the built-in Address Book framework, which isn t related to data storage but has some complexities of its own. SQLite is a compact version of MySQL. Even though it doesn t offer as many field types as MySQL, it s still a powerful method of storage. One of the greatest strengths of an SQLite database is its portability. Unlike MySQL, it doesn t require a
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