Mysteries of Auto Layout, Part 1: https://developer.apple.com/videos/play/wwdc2015/218

Auto Layout Definition: Constraints lead to equations that layout your views automatically

Maintanable Layouts

• Stack View - new to iOS 9
• Arrange views linearly, vertically
• Manages constraints of your subviews
• Horizontal or vertical
• Stack Views are basically for grouping elements together
  • Distribution property - can distribute across the axis
  • Example: Fill, fill equally, fill proportionally, etc.
• Stack View options:
  • Axis: Vertical/horizontal
  • Alignment: Fill (spread itself across entire space)/leading/center/leading
  • Spacing (spacing between elements)
• Can stack within Stack Views
• After everything is stacked within the same Stack, can add constraints so it correctly fills the superview
• Control drag from Stack View to superview to add new constraints that will pin it to the screen edge
• New options: Content hugging priority, content compression resistance priority
• Can resist changing sizes (useful for things like tab menus, buttons, etc.)
• Start with Stack View, use constraints as needed

Changing Constraints

• Don’t add/remove constraints
• Instead, activate and deactivate constraints
• Never deactivate self.view.constraints
  • Weird things will happen
  • Keep references to constraints you need, don’t just blindly deactivate all of them
• Can animate constraints
• Use self.view.layoutIfNeeded

Create size constraints programmably

• intrinsicContentSize = automatically makes the size constraint the same size as the content within the view
• Use proportions — will likely be more successful
• Don’t use points

Constraint Priorities

• Don’t set a constraint as “required”
• Don’t use equal priorities
• Set priorities a little higher or lower than the defaults:
  • Scale from: 1-1000
  • Low: 250
  • High: 750
• This is good for localization — stretching UILabels, etc.

Posted in iOS Development with Swift, Xcode