ios – AutoLayout layoutIfNeeded bounds replace time

I’ve the next code in my customized UIView. This will get known as from init(body:) or init(coder:) initializer:

   non-public func setupContentView() {
     contentView = ContentView(body: .zero)
     contentView.translatesAutoresizingMaskIntoConstraints = false
     addSubview(contentView)
     contentView.leftAnchor.constraint(equalTo: leftAnchor, fixed:thumbWidth).isActive = true
     contentView.rightAnchor.constraint(equalTo: rightAnchor, fixed: -thumbWidth).isActive = true
     contentView.topAnchor.constraint(equalTo: topAnchor).isActive = true
     contentView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
     contentView.clipsToBounds = true
     contentView.isUserInteractionEnabled = true
     contentView.layoutIfNeeded()
     NSLog("ContentView bounds (contentView.bounds), view bounds (self.bounds)")
}

I perceive that when layoutIfNeeded known as, it would replace contentView body as quickly as it’s finished. However I don’t at all times see this behaviour. The NSLog dump beneath reveals that bounds of contentView are nonetheless 0 width and 0 top. What am I lacking?

ContentView bounds (0.0, 0.0, 0.0, 0.0), view bounds (0.0, 0.0, 774.0, 84.0)