Question

我陷入无法找到解决方案的境地。看到很多类似的问题，但无法解决。

所以我有一个View Controller，它显示两种类型的表视图列表

1）销售
2）购买

而且我决定为两者使用相同的View Controller

enum SalesRowType {
    case salesOrderBooking
    case salesInvoicing
    case salesGrossContribution
}

enum PurchaseRowType {
    case purchaseOrders
    case amended_non_amended
    case pending_grn_po
}

和

// BASE PROTOCOL
 // ListRowType -> has title,image property 
protocol HomeSubItemType:ListRowType {
    associatedtype RowType
    var type:RowType {get}
}
// PURCHASE ITEMS

struct PurchaseSubItem: HomeSubItemType {

    typealias RowType = PurchaseRowType

    var image: UIImage
    var title: String
    var type: PurchaseRowType
}
// SALES ITEMS
struct SalesSubItem : HomeSubItemType {
    var image:UIImage
    var title:String
    var type:SalesRowType
}

在我的View Controller中，我想根据销售和购买创建数组

if let type = type {
            switch type {
            case .purchase:
                self.title = "Purchase"
                self.itemList = [
                    PurchaseSubItem(image: UIImage(named: "purchase-orders")!, title: "Purchase Orders", type: .purchaseOrders),
                    PurchaseSubItem(image: UIImage(named: "amended-non")!, title: "Amended/NON-Amended-UNAutho-PO", type: .purchaseOrders),
                    PurchaseSubItem(image: UIImage(named: "purchase-pending")!, title: "Pending GRN PO", type: .purchaseOrders)]

            case .sales:
                self.title = "Sales"

                self.itemList =
                [
                    SalesSubItem(image: UIImage(named: "sales-order-booking")!, title: "Sales Order Booking", type: .salesOrderBooking),
                    SalesSubItem(image: UIImage(named: "sales-invoice")!, title: "Sales Invoicing", type: .salesInvoicing),
                    SalesSubItem(image: UIImage(named: "sale-gross")!, title: "Sales Gross Contribution", type: .salesGrossContribution)]

            default:
                assertionFailure("Only Purchase and sales are handle here")
            }
        }

但是我不能声明数组

var itemList  = [HomeSubItemType]() 
//ERROR HERE

协议“ HomeSubItemType”只能用作一般约束，因为它具有“自我”或相关类型要求

请帮助我解决此问题。预先感谢

Answer 1

更新

这是一个完全不同的解决方案，专注于解决问题而不是使用泛型

首先，我为枚举创建了一个协议，它是空的，因为它只是意味着将它们分组在一起

protocol RowType {}

两个枚举都实现了此功能，此处未显示，我将ListRowType修改为

protocol ListRowType {
    var title: String {get}
    var image: UIImage {get}
    var type: RowType  {get}
}

并完全跳过了HomeSubItemType。

SubItem现在是

struct SubItem: ListRowType {
    var type: RowType
    var title: String
    var image: UIImage   
}

和我的测试代码

var itemList  = [ListRowType]()
let sale = SubItem(type: SalesRowType.salesInvoicing, title: "XYZ", image: UIImage())
itemList.append(sale)

let purchase = SubItem(type: PurchaseRowType.purchaseOrders, title: "ABC", image: UIImage())
itemList.append(purchase)

如果愿意，当然可以将其与原始PurchaseSubItem和SalesSubItem而非SubItem一起使用

我用通用结构替换了这两个结构

struct SubItem<T>: HomeSubItemType {    
    typealias RowType = T

    var type: T
    var title: String
    var image: UIImage
}

并像这样使用它

var itemList  = [SubItem<SalesRowType>]()
var item = SubItem(type: SalesRowType.salesInvoicing, title: "XYZ", image: UIImage())

itemList.append(item)

因此，无论如何，您都需要最好的数组，如果出于某种原因，您必须只声明一个，然后声明它

var itemList  = [Any]()

协议的声明属性显示协议只能用作通用约束，因为它具有自身或相关的类型要求

1 个答案: