如何使 IndexPath rawRepresentable？

Question

我正在尝试重构代码并创建一个枚举类来保存表格视图单元格的 indexPath。

我想让代码这样工作：

enum TableViewCell: IndexPath {
     case shopImageView = [0,0]
     case selectShopImageButton = [0,1]
}

但是编译器说 indexPath 不是 rawRepresentable：

“TableViewCell”声明了原始类型“IndexPath”，但不符合 RawRepresentable 且无法合成一致性

枚举大小写的原始值必须是文字

如何使 indexPath rawRepresentable？代码目前是这样工作的，我想改进它。

enum TableViewCell {
    case shopImageView
    case selectShopImageButton
    case shopNameLocal
    case shopNameEN
    case addressLocal
    case addressEN
    case selectAddressButton
    case openingHours
    case datePickers
    case phone
    case email
    case uploadShopFormButton
    
    var indexPath: IndexPath {
        switch self {
        case .shopImageView:         return [0,0]
        case .selectShopImageButton: return [0,1]
        case .shopNameLocal:         return [0,2]
        case .shopNameEN:            return [0,3]
        case .addressLocal:          return [0,4]
        case .addressEN:             return [0,5]
        case .selectAddressButton:   return [0,6]
        case .openingHours:          return [0,7]
        case .datePickers:           return [0,8]
        case .phone:                 return [0,9]
        case .email:                 return [0,10]
        case .uploadShopFormButton:  return [0,11]
        }
    }
}

Answer 1

使用硬编码TableViewIndexPath 的另一种方法是使用具有静态属性的enum。这样做的好处是，如果您在各种TableView 委托方法中引用了IndexPath，并且您需要更改IndexPath 引用，那么您只需在枚举中更改一次即可。

 private enum TableIndex {
    // Section 0: Information
    static let information =        IndexPath(row: 0, section: 0)
    // Section 1: Preferences
    static let notifications =      IndexPath(row: 0, section: 1)
    static let units =              IndexPath(row: 1, section: 1)
    static let hapticFeedback =     IndexPath(row: 2, section: 1)
    // Section 2: Links
    static let leaveReview =        IndexPath(row: 0, section: 2)
    static let support =            IndexPath(row: 1, section: 2)
    static let privacyPolicy =      IndexPath(row: 2, section: 2)
    static let disclaimer =         IndexPath(row: 3, section: 2)
}

然后您可以像这样引用它们：

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    switch indexPath {
    case TableIndex.information:
        // do something
    case TableIndex.notifications:
        // do something
    case TableIndex.units:
        // do something

        // etc

    default:
        break
    }
}

Answer 2

还有其他方法，但不一定更好，反正你可以把代码剪成这样。

enum TableViewCell: Int  {
    case shopImageView = 0
    case selectShopImageButton = 1
    case shopNameLocal = 2
    case shopNameEN = 3
    case addressLocal
    case addressEN
    case selectAddressButton
    case openingHours
    case datePickers
    case phone
    case email
    case uploadShopFormButton
    
    var indexPath: IndexPath {
        return [0, self.rawValue]
    }
}

另外请记住，这还取决于您如何使用它们，例如您在何处以及如何传递参数。

其中一种方式。

extension IndexPath {
     init(using type: TableViewCell) {
        self.init(row: type.rawValue, section: 0)
    }
}

let indexPath = IndexPath(using: .shopNameEN)

Answer 3

extension IndexPath : RawRepresentable {
    public init?(rawValue: (Int, Int)) {
        self.init(row: rawValue.0, section: rawValue.1)
    }
    public var rawValue: (Int, Int) {
        (self.row, self.section)
    }
}

// We can't use array literal for raw value of an enum, but we can use `String` literal instead.
extension IndexPath: ExpressibleByStringLiteral {
    public init(stringLiteral: StringLiteralType) {
        let a = stringLiteral.split(separator: ",")
        if let row = Int(a[0]), let section = Int(a[1]) {
             self.init(row: row, section: section)
        } else {
            self.init(row: 0, section: 0)
        }
    }
}
// We can use array literals to initialize `IndexPath` but not to define an enum case.
enum TableViewCell: IndexPath {
     case shopImageView = "0,0" // `String` literal
     case selectShopImageButton = "0,1" // `String` literal
}

print(TableViewCell.selectShopImageButton.rawValue)