Discussion
Auto Layout
Stack Views, FTW (Auto Layout without constraints) (New in iOS 9, similar to what’s available in watchOS and NSStackView, which is available from OS X 10.9)
UILayoutGuide
New in iOS 9
Defines a rectangular geometry that can interact with Auto Layout
Eliminates the need (in many cases, at least) for views that are included solely for layout purposes (container views, spacing views, etc)
Views can still provide a greater degree of encapsulation
Provide anchors that can be used to generate constraints
Anatomy of constraints
The layout of your view hierarchy is defined as a series of linear equations. Each constraint represents a single equation. Your goal is to declare a series of equations that has one and only one possible solution.
Two basic types of attributes
Size attributes (for example, Height and Width)
Location attributes (for example, Leading, Left, and Top)
The following rules apply:
You cannot constrain a size attribute to a location attribute.
You cannot assign constant values to location attributes.
You cannot use a nonidentity multiplier (a value other than 1.0) with location attributes.
For location attributes, you cannot constrain vertical attributes to horizontal attributes.
For location attributes, you cannot constrain Leading or Trailing attributes to Left or Right attributes.
Rule of Thumb for clarity
Whole number multipliers are favored over fractional multipliers.
Positive constants are favored over negative constants.
Wherever possible, views should appear in layout order: leading to trailing, top to bottom.
Constraint Priorities
1000 is required
< 1000 is optional
Intrinsic Content Size
Content Compression Resistance
Content Hugging
Debugging Auto Layout
Error Types
Unsatisfiable Layouts. Your layout has no valid solution.
Usually 2 or more required constraints conflict
Ambiguous Layouts. Your layout has two or more possible solutions.
* Need additional constraints
conflicting optional constraints
Logical Errors. There is a bug in your layout logic.
Tips and Tricks
take advantage of the logs
use meaning identifiers on views and constraints
Debug > View Debugging > Show Alignment Rectangles
Picks
Darryl
App Cooker & App Taster - Prototyping tool for Watch, iPhone and iPad apps
Nolan
We Haven’t Forgotten How To Program Enough
John
Mysteries of Auto Layout Part 1 and Part 2 from WWDC 2015
My choice for a smart watch, Fitbit Blaze
