UIViewController extension to support Flutter

UIViewController+Flutter.swift

import UIKit
import Flutter

extension UIViewController {
    
    // 全てのUIViewControllerでフラターを内包できるように関数を定義します。
    private func createFlutterViewController() -> FlutterViewController? {
        if let flutterEngine = (UIApplication.shared.delegate as? AppDelegate)?.informationTabFlutterEngine {
            let flutterViewController = FlutterViewController(engine: flutterEngine, nibName: nil, bundle: nil)
            return flutterViewController
        }
        return nil
    }
    
    //　フラターのUIが何かのサブビューに入るべき場合はこの関数を使います
    private func constrainFlutterView(_ flutterView: UIView, containingView: UIView) {
        flutterView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint(item: flutterView, attribute: NSLayoutConstraint.Attribute.top, relatedBy: NSLayoutConstraint.Relation.equal, toItem: containingView, attribute: NSLayoutConstraint.Attribute.top, multiplier: 1, constant: 0).isActive = true
        NSLayoutConstraint(item: flutterView, attribute: NSLayoutConstraint.Attribute.left, relatedBy: NSLayoutConstraint.Relation.equal, toItem: containingView, attribute: NSLayoutConstraint.Attribute.left, multiplier: 1, constant: 0).isActive = true
        NSLayoutConstraint(item: flutterView, attribute: NSLayoutConstraint.Attribute.right, relatedBy: NSLayoutConstraint.Relation.equal, toItem: containingView, attribute: NSLayoutConstraint.Attribute.right, multiplier: 1, constant: 0).isActive = true
        NSLayoutConstraint(item: flutterView, attribute: NSLayoutConstraint.Attribute.bottom, relatedBy: NSLayoutConstraint.Relation.equal, toItem: containingView, attribute: NSLayoutConstraint.Attribute.bottom, multiplier: 1, constant: 0).isActive = true
    }
    
    // フラター画面を作成する時にこの関数を使います。
    func setupFlutterView(flutterEngine: FlutterEngine,
                          flutterRoute: String?,
                          containingView: UIView,
                          title: String?) -> FlutterViewController {
        let flutterViewController = FlutterViewController(engine: flutterEngine, nibName: nil, bundle: nil)
        flutterViewController.title = title
        if let flutterRoute: String = flutterRoute {
            flutterViewController.pushRoute(flutterRoute)
        }
        flutterViewController.view.frame = containingView.bounds
        containingView.addSubview(flutterViewController.view)
        if containingView != self.view {
            self.constrainFlutterView(flutterViewController.view, containingView: containingView)
        }
        self.addChild(flutterViewController)
        flutterViewController.didMove(toParent: self)
        
        return flutterViewController
    }
}