将struct属性作为通用类型传递

Question

所以我目前有一个将枚举作为类型的结构。下面是具有属性itemType的结构。

struct FormPickerItem: FormItem {
    let id: String
    var title: String
    let itemType: Any.Type
    var margin: UIEdgeInsets
    var size: CGSize?
}

我的枚举的结构如下。

enum UserGoal {
    case all
    case buildMuscle
    case strength
    case none
}

extension UserGoal: EnumItem {

    typealias RawValue = String

    init?(rawValue: RawValue) {
        switch rawValue {
        case "All": self = .all
        case "Build Muscle": self = .buildMuscle
        case "Strength": self = .strength
        case "None": self = .none
        default: return nil
        }
    }

    var rawValue: RawValue {
        switch self {
        case .all: return "All"
        case .buildMuscle: return "Build Muscle"
        case .strength: return "Strength"
        case .none: return "None"
        }
    }
}

此结构是使用以下代码创建的，您可以看到itemType是我正在传递的枚举类型。

FormPickerItem(id: "userGoals", title: "Goals", itemType: UserGoal.self, margin: UIEdgeInsets(top: 0, left: 30, bottom: 0, right: 30), size: nil)

EnumItem是一个协议，所有枚举都在子类化中，因此我可以轻松地将任何枚举作为通用类型传递给我拥有的自定义类。因此，我目前遇到的问题是我无法将结构中的属性作为通用类型传递。

func configure(with formPickerItem: FormPickerItem, atIndex index: Int = 0, toolBarType: ToolBarType? = .standard, delegate: FormTextFieldDelegate?) {
    self.formPickerItem = formPickerItem
    self.index = index
    self.toolBarType = toolBarType
    self.delegate = delegate

    if loftyPicker == nil {

        loftyPicker = LoftyPicker<formPickerItem.itemType>(index: index, title: formPickerItem.title, applyBottomBorder: true, parentView: self.contentView, loftyDelegate: self)
        contentView.addSubview(loftyPicker!)
        applyConstraints()
    }
}

并且这样声明LoftyPicker类。

final class LoftyPicker<Item: EnumItem>: LoftyBaseTextField, UIPickerViewDelegate, UIPickerViewDataSource, LoftyToolBarDelegate {
....
}

我收到以下错误Use of undeclared type 'formPickerItem'。这可能很快吗？如果没有，如何将枚举类型传递给类？