Swift 4, custom UIView with explanations

customView.swift

class MyCustomView: UIView {
    
    private var didSetupConstraints = false

    //In Swift initializers are not inherited for subclasses by default
    override init(frame: CGRect) {
        super.init(frame: frame)
    }
    
    // Deserialize your object here
    // required = subclasses of that class have to implement it too
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    
    //    There are 3 phases to displaying a view:
    //    update constraints
    //    update layout
    //      layoutSubviews
    //    update display
    //    draw Rect
    
    //its called when
    //Its own bounds (not frame) changed
    //The bounds of one of its direct subviews changed
    //A subview is added to the view or removed from the view
    //set the frame rectangles of your subviews directly
    //setNeedsLayout(): If you want to force a layout update, call the setNeedsLayout() method instead to do so prior to the next drawing update.
    //layoutIfNeeded(): If you want to update the layout of your views immediately, call the layoutIfNeeded() method
    //use both setNeedsLayouts - layoutIfNeeded for instant use
    override func layoutSubviews() {
        super.layoutSubviews()
        
        //myProperty.frame = CGRect...
        // intrinsic content size changes
        
        // super.layoutSubviews() The second call to super.layoutSubviews() is optional but may be required 
			  //if the intrinsic conent size of the view changes
    }
    
    //update AutoLayoutConstrains here
    //runs more than once
    //CAREFUL don't add new constrains - update the existent one
    override func updateConstraints() {
        if didSetupConstraints == false {
            configureAutolayoutConstrains()
        }
        
        super.updateConstraints()
    }
    
    //put here your initial autoLayout Setup
    private func configureAutolayoutConstrains () {
        
    }
    
    //Each UIView subclass should implement the intrinsicContentSize 
    //and return the size that it thinks its ok for it.
    //If we didn’t know how wide the view is we 
    //would use UIViewNoIntrinsicMetric instead of the width
    final override var intrinsicContentSize: CGSize {
   	return CGSize(width: UIView.noIntrinsicMetric, height: 20)
    }
	
    //is called immediately before a class instance is deallocated.
    //cleanup yourself your own resources
    //close filemanagers, remove observers etc
    deinit {
        
    }
}