Result of 'HStack' initializer is unused / HStack Not Appearing in View

Question

I'm trying to get an HStack of stars for rating (1-5) to appear in a view that I've created, but I'm getting this warning Result of 'HStack<Content>' initializer is unused and the stars aren't appearing on the view.

AddMeal View Code:

import SwiftUI

class AddMeal: UIViewController {
    @State var stars = -1

    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .red
        
        // Add Meal Title Label
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
        label.center = self.view.center
        label.center.x = self.view.center.x
        label.center.y = 75
        label.font = label.font.withSize(30);
        label.textAlignment = .center
        label.textColor = .white
        label.text = "Add Meal"
        self.view.addSubview(label)
        
        // Meal Title Label
        let food = UILabel(frame: CGRect(x: 22, y: 100, width: 200, height: 50))
        food.font = label.font.withSize(20);
        food.textColor = .white
        food.text = "Meal Title"
        self.view.addSubview(food)
        
        // Food Title Input Text Field
        let sampleTextField =  UITextField(frame: CGRect(x: 20, y: 150, width: 335, height: 40))
        sampleTextField.placeholder = "Enter the Name of the Food or Drink..."
        sampleTextField.font = UIFont.systemFont(ofSize: 15)
        sampleTextField.borderStyle = UITextField.BorderStyle.roundedRect
        sampleTextField.autocorrectionType = UITextAutocorrectionType.no
        sampleTextField.keyboardType = UIKeyboardType.default
        sampleTextField.returnKeyType = UIReturnKeyType.done
        sampleTextField.clearButtonMode = UITextField.ViewMode.whileEditing
        sampleTextField.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
        self.view.addSubview(sampleTextField)
        
        // Meal Calories Label
        let mealCalories = UILabel(frame: CGRect(x: 22, y: 200, width: 200, height: 50))
        mealCalories.font = label.font.withSize(20);
        mealCalories.textColor = .white
        mealCalories.text = "Meal Calories"
        self.view.addSubview(mealCalories)
        
        // Calories Input Text Field
        let sampleTextField2 =  UITextField(frame: CGRect(x: 20, y: 250, width: 335, height: 40))
        sampleTextField2.placeholder = "Enter the # of Calories..."
        sampleTextField2.font = UIFont.systemFont(ofSize: 15)
        sampleTextField2.borderStyle = UITextField.BorderStyle.roundedRect
        sampleTextField2.autocorrectionType = UITextAutocorrectionType.no
        sampleTextField2.keyboardType = UIKeyboardType.default
        sampleTextField2.returnKeyType = UIReturnKeyType.done
        sampleTextField2.clearButtonMode = UITextField.ViewMode.whileEditing
        sampleTextField2.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
        self.view.addSubview(sampleTextField2)
        
        // Meal Rating Label
        let mealRating = UILabel(frame: CGRect(x: 22, y: 300, width: 200, height: 50))
        mealRating.font = label.font.withSize(20);
        mealRating.textColor = .white
        mealRating.text = "Meal Rating"
        self.view.addSubview(mealRating)
        
        // Rating Stars
        HStack {
            ForEach(0..<5){ i in
                
                Image(systemName: "star.fill").resizable().frame(width: 30, height:30).foregroundColor(self.stars >= i ? .yellow : .gray).onTapGesture {
                    self.stars = i
                }
            }
        }
    }
    
}

Current Output Image:

Output

Does anyone know how I can address this warning and get my HStack of stars to appear on the screen properly?

You can use SwiftUI code in SwiftUI structs only. You can't use them in UIViewController. See https://developer.apple.com/tutorials/swiftui/ — pawello2222, Dec 24 '20 at 21:44

Asperi · Answer 1 · 2020-12-25T03:42:59.820

We can separate SwiftUI code into standalone view and then integrate it into view controller using UIHostingController.

Here is a demo of possible solution. Tested with Xcode 12.1 / iOS 14.1 (of course you can tune layout as you need)

class AddMeal: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .red
        
        // Add Meal Title Label
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
        label.center = self.view.center
        label.center.x = self.view.center.x
        label.center.y = 75
        label.font = label.font.withSize(30);
        label.textAlignment = .center
        label.textColor = .white
        label.text = "Add Meal"
        self.view.addSubview(label)
        
        // Meal Title Label
        let food = UILabel(frame: CGRect(x: 22, y: 100, width: 200, height: 50))
        food.font = label.font.withSize(20);
        food.textColor = .white
        food.text = "Meal Title"
        self.view.addSubview(food)
        
        // Food Title Input Text Field
        let sampleTextField =  UITextField(frame: CGRect(x: 20, y: 150, width: 335, height: 40))
        sampleTextField.placeholder = "Enter the Name of the Food or Drink..."
        sampleTextField.font = UIFont.systemFont(ofSize: 15)
        sampleTextField.borderStyle = UITextField.BorderStyle.roundedRect
        sampleTextField.autocorrectionType = UITextAutocorrectionType.no
        sampleTextField.keyboardType = UIKeyboardType.default
        sampleTextField.returnKeyType = UIReturnKeyType.done
        sampleTextField.clearButtonMode = UITextField.ViewMode.whileEditing
        sampleTextField.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
        self.view.addSubview(sampleTextField)
        
        // Meal Calories Label
        let mealCalories = UILabel(frame: CGRect(x: 22, y: 200, width: 200, height: 50))
        mealCalories.font = label.font.withSize(20);
        mealCalories.textColor = .white
        mealCalories.text = "Meal Calories"
        self.view.addSubview(mealCalories)
        
        // Calories Input Text Field
        let sampleTextField2 =  UITextField(frame: CGRect(x: 20, y: 250, width: 335, height: 40))
        sampleTextField2.placeholder = "Enter the # of Calories..."
        sampleTextField2.font = UIFont.systemFont(ofSize: 15)
        sampleTextField2.borderStyle = UITextField.BorderStyle.roundedRect
        sampleTextField2.autocorrectionType = UITextAutocorrectionType.no
        sampleTextField2.keyboardType = UIKeyboardType.default
        sampleTextField2.returnKeyType = UIReturnKeyType.done
        sampleTextField2.clearButtonMode = UITextField.ViewMode.whileEditing
        sampleTextField2.contentVerticalAlignment = UIControl.ContentVerticalAlignment.center
        self.view.addSubview(sampleTextField2)
        
        // Meal Rating Label
        let mealRating = UILabel(frame: CGRect(x: 22, y: 300, width: 200, height: 50))
        mealRating.font = label.font.withSize(20);
        mealRating.textColor = .white
        mealRating.text = "Meal Rating"
        self.view.addSubview(mealRating)
        
        // Rating Stars
        let stars = UIHostingController(rootView: StarsView())
        self.view.addSubview(stars.view)
        self.addChild(stars)
        stars.view.backgroundColor = .clear

        stars.view.translatesAutoresizingMaskIntoConstraints = false
        stars.view.sizeToFit()
        stars.view.topAnchor.constraint(equalTo: mealRating.bottomAnchor, constant: 25).isActive = true
        stars.view.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
    }
}

struct StarsView: View {
    @State var stars = -1
    var body: some View {
        HStack {
            ForEach(0..<5){ i in
                Image(systemName: "star.fill")
                    .resizable().frame(width: 30, height:30)
                    .foregroundColor(self.stars >= i ? .yellow : .gray)
                    .onTapGesture {
                        self.stars = i
                    }
            }
        }
    }
}

score 0 · Answer 2 · answered Dec 24 '20 at 22:14

0

You have to use UIStackView instead of HStack(SwiftUI) in UIKit Pattern.

UIStackView has axis that indicate horizontal or vertical.

stackView.axis = .Horizontal

Please reference this url. https://developer.apple.com/documentation/uikit/uistackview

answered Dec 24 '20 at 22:14

Harry Jin

54
7

Result of 'HStack' initializer is unused / HStack Not Appearing in View

2 Answers2