[Swift] lazy 속성과 self-executing 의 활용

collectionView 초기화를 아래와 같이 클로저로서 생성이 가능하다.

.....이런게 되다니!! 멋져 ❤️

class ItemsViewController: UIViewController {
    private lazy var collectionView: UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        let view = UICollectionView(frame: self.view.bounds, collectionViewLayout: layout)
        view.delegate = self
        view.dataSource = self
        return view
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(collectionView)
    }
}