Priority

priority.swift

import UIKit
import SnapKit_Sources
import PlaygroundSupport

final class TestView: UIView {

    let labelPrimary: UILabel = {
        let label = UILabel()
        label.font = UIFont.systemFont(ofSize: 25)
        label.textColor = .black
        label.text = "Primary Text"
        label.textAlignment = .center
        return label
    }()
    
    let labelSecondary: UILabel = {
        let label = UILabel()
        label.font = UIFont.systemFont(ofSize: 14)
        label.textColor = .blue
        label.textAlignment = .center
        return label
    }()
    
    init(secondary: String?) {
        super.init(frame: .zero)
        
        labelSecondary.text = secondary
        
        addSubview(labelSecondary)
        labelSecondary.snp.makeConstraints { (make) in
            make.left.equalToSuperview()
            make.right.equalToSuperview()
            make.top.equalToSuperview()
        }
        
        addSubview(labelPrimary)
        labelPrimary.snp.makeConstraints { (make) in
            make.left.equalToSuperview()
            make.right.equalToSuperview()
            make.top.equalTo(labelSecondary.snp.bottom).priority(251)
            make.bottom.equalToSuperview()
        }
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}
    
final class MyViewController: UIViewController {
    
    private let view1: TestView = {
        let view = TestView(secondary: "Secondary Text")
        view.backgroundColor = .gray
        return view
    }()
    
    private let view2: TestView = {
        let view = TestView(secondary: nil)
        view.backgroundColor = .gray
        return view
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        setupUI()
    }
    
    /// Setup UI elements
    private func setupUI() {
        view1.frame = CGRect(x: 50, y: 100, width: 200, height: 50)
        view.addSubview(view1)
        view2.frame = CGRect(x: 50, y: 200, width: 200, height: 50)
        view.addSubview(view2)
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(true)
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(true)
        dump("labelPrimary => \(view2.labelPrimary.constraints)")
        print("==============")
        dump("labelSecondary => \(view2.labelSecondary.constraints)")
    }
}


let vc = MyViewController()
let frame = CGRect(x: 0, y: 0, width: 768, height: 1024)
let window = UIWindow(frame: frame)
window.rootViewController = vc
window.makeKeyAndVisible()
PlaygroundPage.current.liveView = vc