Adding DynamicForms

FormViewController.swift

//
//  ViewController.swift
//  FormConfig
//
//  Created by Damodar Namala on 01/08/23.
//

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }
    
    @IBAction func next() {
        let vc = FormView.buildForm()
        self.present(vc, animated: true)
    }
}


class FormViewModel {
    var configuration: FormView.Configuration
    init(configuration: FormView.Configuration) {
        self.configuration = configuration
    }
}

class FormViewController: UIViewController {
    var continer: UIStackView = {
        let stack = UIStackView(frame: .zero)
        stack.axis = .vertical
        stack.alignment = .leading
        stack.translatesAutoresizingMaskIntoConstraints = false
        return stack
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .lightGray.withAlphaComponent(0.15)
        self.view.addSubview(continer)
        NSLayoutConstraint.activate([
            self.continer.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 16),
            self.continer.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -16),
            self.continer.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 16),
            self.continer.bottomAnchor.constraint(lessThanOrEqualTo: self.view.bottomAnchor, constant: -16),
        ])
        
        self.viewModel.configuration.steps.lazy.forEach { step in
            switch step {
            case .from(let controller):
                self.addChildViewController(child: controller)
            case .to(let controller):
                self.addChildViewController(child: controller)
            case .amount(let controller):
                self.addChildViewController(child: controller)
            }
        }
    }
    
    func addChildViewController(child: UIViewController) {
        child.willMove(toParent: self)
        self.addChild(child)
        continer.addArrangedSubview(child.view)
        child.willMove(toParent: self)
    }
    
    var viewModel: FormViewModel
    
    init(viewModel: FormViewModel) {
        self.viewModel = viewModel
        super.init(nibName: nil, bundle: nil)
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("\(#function) has not been implemented")
    }
}

struct FormView {
    private init() {}
    static func buildForm() -> UIViewController {
       
        let viewModel = FormViewModel(configuration: .init(steps: [
            .amount(FormView.buildAmountController()),
            .from(FormView.buildFromAccountController()),
            .to(FormView.buildToAccountController()),
        ]))
        
       return FormViewController(viewModel: viewModel)
    }
    
    static func buildFromAccountController() -> UIViewController {
        FromViewController()
    }
    
    static func buildToAccountController() -> UIViewController {
        ToViewController()
    }
    
    static func buildAmountController() -> UIViewController {
        AmountViewController()
    }
    
}

extension FormView {
    struct Configuration {
        var steps: [FormField] = [
            .from(FormView.buildFromAccountController()),
            .to(FormView.buildToAccountController()),
            .amount(FormView.buildAmountController())
        ]
    }
}

public enum FormField {
    case from(UIViewController)
    case to(UIViewController)
    case amount(UIViewController)
}


class FromViewController: UIViewController {
    var label: UILabel = {
        let view = UILabel(frame: .zero)
        view.font = .preferredFont(forTextStyle: .largeTitle)
        view.textColor = .red
        view.translatesAutoresizingMaskIntoConstraints = false
        view.text  = "FromView"
        view.textAlignment = .center
        return view
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .lightGray.withAlphaComponent(0.15)
        self.view.addSubview(label)
        NSLayoutConstraint.activate([
            self.label.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 16),
            self.label.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -16),
            self.label.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 16),
            self.label.bottomAnchor.constraint(lessThanOrEqualTo: self.view.bottomAnchor, constant: -16),
        ])
    }
    
    
    init() {
        super.init(nibName: nil, bundle: nil)
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("\(#function) has not been implemented")
    }
}

class ToViewController: UIViewController {
    var label: UILabel = {
        let view = UILabel(frame: .zero)
        view.font = .preferredFont(forTextStyle: .largeTitle)
        view.textColor = .red
        view.translatesAutoresizingMaskIntoConstraints = false
        view.text  = "ToView"
        view.textAlignment = .center
        return view
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .lightGray.withAlphaComponent(0.15)
        self.view.addSubview(label)
        NSLayoutConstraint.activate([
            self.label.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 16),
            self.label.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -16),
            self.label.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 16),
            self.label.bottomAnchor.constraint(lessThanOrEqualTo: self.view.bottomAnchor, constant: -16),
        ])
    }
    
    init() {
        super.init(nibName: nil, bundle: nil)
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("\(#function) has not been implemented")
    }
}

class AmountViewController: UIViewController {
    
    var label: UILabel = {
        let view = UILabel(frame: .zero)
        view.font = .preferredFont(forTextStyle: .largeTitle)
        view.textColor = .red
        view.translatesAutoresizingMaskIntoConstraints = false
        view.text  = "AmountView"
        view.textAlignment = .center
        return view
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .lightGray.withAlphaComponent(0.15)
        self.view.addSubview(label)
        NSLayoutConstraint.activate([
            self.label.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 16),
            self.label.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -16),
            self.label.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 16),
            self.label.bottomAnchor.constraint(lessThanOrEqualTo: self.view.bottomAnchor, constant: -16),
        ])
    }
    
    
    init() {
        super.init(nibName: nil, bundle: nil)
    }
    
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("\(#function) has not been implemented")
    }
}