107: Hit the TIE Fighter

iOhYes

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