Item Source Callbacks
Recipe 11-4 passes self to the controller as part of its items array. self adopts the source protocol (<UIActivityItemSource>), so the controller understands to use callbacks when retrieving data items. The callback methods enable you to vary your data based on each one’s intended use. Use the activity types (such as Facebook or Add to Contacts; they’re listed earlier in this section) to choose the exact data you want to provide. This is especially important when selecting from resolutions for various uses. When printing, keep your data quality high. When tweeting, a low-res image may do the job instead.
If your data is invariant—that is, you’ll be passing the same data to e-mail as you would to Facebook—you can directly ...
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