Simplest iOS Checkbox (UIKit)

CheckboxButton.swift

import UIKit

/// Checkbox with title. When checked, `isSelected` is `true`.
class CheckboxButton: UIButton {
    /// Handler called when the checkbox is checked or unchecked
    var onCheck: ((Bool) -> Void)?

    /// - Parameters:
    ///   - title: Text shown next to the checkbox
    ///   - color: Color for both checkbox and title
    ///   - normalImage: Unchecked image (default is empty square)
    ///   - selectedImage: Checked image (default is square with V)
    ///   - spacing: Space between checkbox and title
    ///   - direction: Layout direction
    ///   - onCheck: Handler to call when the checkbox is checked or unchecked
    init(
        title: String? = nil,
        color: UIColor? = nil,
        normalImage: UIImage = UIImage(systemName: "square")!,
        selectedImage: UIImage = UIImage(systemName: "checkmark.square.fill")!,
        spacing: CGFloat = 8,
        direction: UIUserInterfaceLayoutDirection = UIApplication.shared.userInterfaceLayoutDirection,
        onCheck: ((Bool) -> Void)? = nil
    ) {
        super.init(frame: .zero)
        self.onCheck = onCheck
        setTitle(title, for: .normal)
        if let color {
            tintColor = color
        }
        setup(normalImage: normalImage, selectedImage: selectedImage, spacing: spacing, direction: direction)
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

    override func didMoveToSuperview() {
        // align imageView to top
        guard let superview, let imageView else { return }
        guard imageView.translatesAutoresizingMaskIntoConstraints else { return }
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.firstBaselineAnchor.constraint(equalTo: firstBaselineAnchor).isActive = true
    }

    @objc private func toggleCheckbox() {
        isSelected.toggle()
        onCheck?(isSelected)
    }

    private func setup(
        normalImage: UIImage = UIImage(systemName: "square")!,
        selectedImage: UIImage = UIImage(systemName: "checkmark.square.fill")!,
        spacing: CGFloat = 8,
        direction: UIUserInterfaceLayoutDirection = UIApplication.shared.userInterfaceLayoutDirection
    ) {
        addTarget(self, action: #selector(toggleCheckbox), for: .primaryActionTriggered)
        setImage(normalImage, for: .normal)
        setImage(selectedImage, for: .selected)

        semanticContentAttribute = direction == .leftToRight ? .forceLeftToRight : .forceRightToLeft

        if #available(iOS 15.0, *) {
            configuration = .plain().updated(for: self)
            configuration?.imagePadding = spacing
            configuration?.contentInsets = .zero
            configuration?.background.backgroundColor = .clear
        } else {
            if direction == .leftToRight {
                contentEdgeInsets = .init(top: 0, left: 0, bottom: 0, right: spacing)
                titleEdgeInsets = UIEdgeInsets(top: 0, left: spacing, bottom: 0, right: -spacing)
            } else {
                contentEdgeInsets = .init(top: 0, left: spacing, bottom: 0, right: 0)
                titleEdgeInsets = UIEdgeInsets(top: 0, left: -spacing, bottom: 0, right: spacing)
            }
        }
    }
}