Difference between Compact and Regular size class

Question

I was watching WWDC 2014 411_Whats_new_in_interface_builder session video.On that video the speaker Kevin Cathey told about size classes.He told that there are 2 size classes have 2 values Compact and Regular.He told to think the size class in terms of magnitude of ViewController.He showed an example on Adapting the bar height with respect to four possible combination of size classes.Actually, i couldn't understand the difference what he was trying to talk about I have three questions: 1. What is Compact and Regular Size classes 2. Why size class is useful? 3. How the four combinations of size class affect on simulator(iPhone 5 and 5s etc)? Thanks, Riduan

Answer 1

From Apple Docs:

Size classes are traits assigned to a user interface element, such as a screen or a view. There are two types of size classes in iOS 8: regular and compact. A regular size class denotes either a large amount of screen space, such as on an iPad, or a commonly adopted paradigm that provides the illusion of a large amount of screen space, such as scrolling on an iPhone. Every device is defined by a size class, both vertically and horizontally.

I like to think of them this way: Regular Size Classes : Big screen. Ipad has a regular vertical and regular horizontal size class. Compact Size Classes : Little. In portrait, an iPhone has a compact size class vertically and a regular size class horizontally

If you go into storyboards and enable size classes, you can design for different screens. Do the bulk of your design in the wAnyhAny size class. If you want something specific for the iphone, change the size classes. In the image below if I select Compact Width/Regular Height (as shown), my View in the Storyboard would change to look like an iphone. I could drag in a label, and that label would only show up on iphones in portrait. If I rotate to landscape the label would not appear because it's a different size class.

You can change four things in a size class:

1. The constant for a constraint
2. If a constraint is installed in the view hierarchy
3. If a view is installed in the view hierarchy
4. The font used for many types of views showing text