A modal dialog demands attention; while it is present, the user can do nothing other than work within it or dismiss it. This chapter discusses various forms of modal dialog:
Within your app, you might want to interrupt things to give the user some information or to ask the user how to proceed. For this purpose, iOS provides two types of rudimentary modal dialog — alerts and action sheets. An alert is basically a message, possibly with an opportunity for text entry, and some buttons. An action sheet is effectively a column of buttons.
You can provide a sort of action sheet even when your app is not frontmost (or even running) by allowing the user to summon quick actions — also known as shortcut items — by pressing with 3D touch on your app’s icon.
A local notification is an alert that the system presents at a predetermined time or place on your app’s behalf, even when your app isn’t frontmost.
A today extension lets your app present interface on the Today side of the device’s notification center. New in iOS 10, a today extension can also appear in the search interface and as a quick action.
An activity view is a modal dialog displaying icons representing possible courses of action, and intended in certain circumstances to replace the action sheet. For example, Mobile Safari’s Share button presents an activity view whose icons represent possible operations on a URL, such as handing it off to Mail, Message, or Twitter, or saving it internally as ...