medium_BottomSheetViewController_2.swift

class BottomSheetViewController: UIViewController {
    // ...
    private var minTopSpacing: CGFloat = 80
    
    // MARK: - View Setup
    override func viewDidLoad() {
        super.viewDidLoad()
        setupViews()
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        animatePresent()
    }
    
    private func setupViews() {
        view.backgroundColor = .clear
        view.addSubview(dimmedView)
        NSLayoutConstraint.activate([
            // Set dimmedView edges to superview
            dimmedView.topAnchor.constraint(equalTo: view.topAnchor),
            dimmedView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            dimmedView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            dimmedView.trailingAnchor.constraint(equalTo: view.trailingAnchor)
        ])

        // Container View
        // All sides are set without spacing, except the top edge have a minimum space 
        // So the bottom sheet view won't go higher
        view.addSubview(mainContainerView)
        NSLayoutConstraint.activate([
            mainContainerView.topAnchor.constraint(greaterThanOrEqualTo: view.topAnchor, constant: minTopSpacing)
            mainContainerView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            mainContainerView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            mainContainerView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        ])
        
        // Top draggable bar view
        mainContainerView.addSubview(topBarView)
        NSLayoutConstraint.activate([
            topBarView.topAnchor.constraint(equalTo: mainContainerView.topAnchor),
            topBarView.leadingAnchor.constraint(equalTo: mainContainerView.leadingAnchor),
            topBarView.trailingAnchor.constraint(equalTo: mainContainerView.trailingAnchor),
            topBarView.heightAnchor.constraint(equalToConstant: 54)
        ])
        // Add fancy bar line
        topBarView.addSubview(barLineView)
        NSLayoutConstraint.activate([
            barLineView.centerXAnchor.constraint(equalTo: topBarView.centerXAnchor),
            barLineView.topAnchor.constraint(equalTo: topBarView.topAnchor, constant: 8),
            barLineView.widthAnchor.constraint(equalToConstant: 40),
            barLineView.heightAnchor.constraint(equalToConstant: 6)
        ])
        
        // Content View
        // This is where content can be dynamically set
        mainContainerView.addSubview(contentView)
        contentView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            contentView.leadingAnchor.constraint(equalTo: mainContainerView.leadingAnchor, constant: 24),
            contentView.trailingAnchor.constraint(equalTo: mainContainerView.trailingAnchor, constant: -24),
            contentView.topAnchor.constraint(equalTo: topBarView.bottomAnchor, constant: 16),
            contentView.bottomAnchor.constraint(equalTo: mainContainerView.bottomAnchor, constant: -32)
        ])
    }
}