UIKit+ResultBuilder.swift

gistfile1.txt

import UIKit
@resultBuilder
struct SubviewBuilder {
    static func buildEither(first component: UIView) -> UIView {
        print(#function + "2")
        return component
    }
    
    static func buildEither(second component: UIView) -> UIView {
        print(#function + "1")
        return component
    }
    static func buildBlock(_ components: UIView...) -> UIView {
        print(#function  + "2" + components.map { $0.tag }.description)
        let view = IfBlockView()
        components.forEach { view.addSubview($0) }
        return view
    }
    static func buildBlock(_ components: UIView...) -> [UIView] {
        print(#function + "1" + components.map { $0.tag }.description)
        let result = components.flatMap {
            if $0 is IfBlockView {
                return $0.subviews
            } else {
                return [$0]
            }
        }
        return result
    }
    static func buildOptional(_ component: UIView?) -> UIView {
        print(#function + "2" + (component?.description ?? "-") ?? "-")
        return component ?? UIView()
    }
    static func buildIf(_ component: UIView?) -> [UIView] {
        print(#function)
        switch component {
        case .none:
            return []
        case .some(let wrapped):
            return [wrapped]
        }
    }
}

class IfBlockView: UIView { }

extension UIView {
    func addSubviews(@SubviewBuilder builder: () -> [UIView]) -> UIView {
        builder().forEach { addSubview($0) }
        return self
    }
}

extension UIView {
    convenience init(tag: Int) {
        self.init(frame: .zero)
        self.tag = tag
    }
}


class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubviews {
            UILabel(tag: 10)
            UILabel(tag: 11)
            
            UILabel(tag: 12)
            
            if 1 == 1 {
                UILabel(tag: 13)
                UILabel(tag: 14)
                UILabel(tag: 16)
                UIView(tag: 30).addSubviews {
                    UILabel(tag: 140)
                    UILabel(tag: 160)
                }
            }
            else {
               UILabel(tag: 15)
            }
            
            if true {
                UILabel(tag: 20)
                UILabel(tag: 21)
                UILabel(tag: 22)
            }
#if RELEASE
            if true {
                
            }
#endif
        }
        print(view.subviews.map { $0.tag })
    }
}