IOS final 4

called after the controller's view is loaded into memory. 

it programmatically layouts the user interface 

in code, it places the frame for each view in a view hierarchy

only called once which is when the app loads

useful for connecting a UI object to a custom

can be a framework-provided control or label or a custom view.

they provide a getter and an optional setter to retrieve and set other properties and values indirectly.

The content view of a UITableViewCell object is the default superview for content displayed by the cell. If you want to customize cells by simply adding additional views, you should add them to the content view so they will be positioned appropriately as the cell transitions into and out of editing mode.

are reusable solutions to common problems in software design. They're templates designed to help you write code that's easy to understand and reuse. They also help you create loosely coupled code so that you can change or replace components in your code without too much hassle.

A scene represents a view controller in the storyboard

• represents the screen
• your app has at this time.

Optional chaining is a process for querying and calling properties, methods, and subscripts on an optional that might currently be nil

observe and respond to changes in a property's value

supplies minimal information about the tableview's appearance.

subclass of UIScrollView , which allows users to scroll through the table, although UITableView allows vertical scrolling only.

must research

By using unwind segue we can navigate backward from one screen to another screen