5.14. Multiple Choice: Pickers, Lists, and Action Sheets

Even better in some cases than choosing the right keyboard is getting rid of the keyboard completely. Remember the dreaded high-school pop quiz? And how much easier it was when it was multiple choice instead of short answer? A limited set of options, all displayed in front of you, made for a better shot at dodging wrong answers. You didn't even have to strain your delicate adolescent wrist to write anything out; you just picked your answer and moved on. The same considerations apply to iPhone apps: picking from a menu of options is faster and less error prone than pecking out the full text on the keyboard. Wherever appropriate, put the keyboard away and give your grateful users a quick-tap menu of options to choose from. The standard iPhone controls include a few different tools to do exactly that.

The picker control installs slot-machine dials in your app to let people "spin to win," choosing from a set of options. The picker can consist of a single wheel, or you can squeeze several wheels side by side to ask your audience for several values at once. Pickers can (and should) include an optional selection bar, a translucent strip that hovers above the dials to make it completely clear which option is selected, and which can also display the units you're working with. Apps typically either fix pickers onscreen as a primary interface element, like the timer function in the Clock app, or keep it tucked away until summoned like a keyboard, skittering up from screen bottom when you tap a button or table cell to enter a value.