How to adjust layouts based on Autolayout Size Classes

SwiftAutolayoutSizeClasses.swift

#!/usr/bin/swift

# Take from Apple Sample Code
# https://developer.apple.com/library/prerelease/ios/samplecode/AdaptivePhotos/Listings/AdaptiveCode_AdaptiveCode_OverlayView_swift.html

class SomeView: UIView {

    override func intrinsicContentSize() -> CGSize {
        var size = label.intrinsicContentSize()
        
        // Add a horizontal margin whose size depends on our horizontal size class.
        if traitCollection.horizontalSizeClass == .Compact {
            size.width += 8.0
        }
        else {
            size.width += 40.0
        }
        
        // Add a vertical margin whose size depends on our vertical size class.
        if traitCollection.verticalSizeClass == .Compact {
            size.height += 8.0
        }
        else {
            size.height += 40.0
        }
        
        return size
    }
    
    override func traitCollectionDidChange(previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)
 
        guard traitCollection.verticalSizeClass != previousTraitCollection?.verticalSizeClass ||
              traitCollection.horizontalSizeClass != previousTraitCollection?.horizontalSizeClass else { return }
        
        /*
            If our size class has changed, then our intrinsic content size will
            need to be updated.
        */
        invalidateIntrinsicContentSize()
    }
}