UIKit_Essentialsチュートリアル

//UICellAccessory.CustomVIewConfigurationを返す関数
private func doneButtonConfiguration(for reminder: Reminder) -> UICellAccessory.CustomViewConfiguration {
        let symbolName = reminder.isComplete ? "circle.fill" : "circle"
        let symbolConfiguration = UIImage.SymbolConfiguration(textStyle: .title1)
        let image = UIImage(systemName: symbolName, withConfiguration: symbolConfiguration)
        let button = UIButton()
        button.setImage(image, for: .normal)
        return UICellAccessory.CustomViewConfiguration(customView: button, placement: .leading(displayed: .always))
    }

cell.accessories = [.customView(configuration: doneButtonConfiguration), disclosureIndidator(displayed: .always)]