将计算变量传递给另一个视图

Question

我正在尝试创建自己的网格，它可以调整每个元素的大小。没关系。这是一个代码

GeometryReader { geo in
            let columnCount = Int((geo.size.width / 250).rounded(.down))
            let tr = CDNresponse.data?.first?.translations ?? []
            let rowsCount = (CGFloat(tr.count) / CGFloat(columnCount)).rounded(.up)
            LazyVStack {
                ForEach(0..<Int(rowsCount), id: \.self) { row in // create number of rows
                    HStack {
                        ForEach(0..<columnCount, id: \.self) { column in // create columns
                            let index = row * columnCount + column
                            if index < (tr.count) {
                                VStack {
                                    MovieCellView(index: index, tr: tr, qualities: $qualities)
                                }
                            }
                        }
                    }
                }
            }
        }

但由于我不知道元素的确切数量及其索引，我需要在视图中计算它们。

let index = row * columnCount + column

这就是问题所在 - 如果我在索引更改时像往常一样传递它们 (MovieCellView(index: index ... ))，则新值不会传递给视图。 我不能使用@State 和@Binding，因为我不能直接在 View Builder 中声明它，也不能在 struct 上声明它，因为我不知道计数。如何正确传递数据？

MovieCellView的代码：

struct MovieCellView: View {
    @State var index: Int
    @State var tr: [String]
    @State var showError: Bool = false
    @State var detailed: Bool = false
    
    @Binding var qualities: [String : [Int : URL]]
    
    var body: some View {
        ...
    }
    
}

最简单的例子 刚刚在带有 MovieCellView 的 VStack 中添加了 Text("\(index)")，在 MovieCellView 正文中添加了 Text("\(index)")。 VStack 中的索引总是在变化，但在 MovieCellView 中没有。 有必要澄清一下，我的应用程序是在 macOS 上并且窗口已调整大小

Answer 1

这是我对您将计算变量传递到另一个视图的问题的解决方案（测试代码）。 我使用 ObservableObject 来存储实现目标所需的信息。

import SwiftUI

@main
struct TestApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

class MovieCellModel: ObservableObject {
    @Published var columnCount: Int = 0
    @Published var rowCount: Int = 0
    
    // this could be in the view 
    func index(row: Int, column: Int) -> Int {
        return row * columnCount + column
    }
}

struct ContentView: View {
    @StateObject var mcModel = MovieCellModel()
    @State var qualities: [String : [Int : URL]] = ["":[1: URL(string: "https://example.com")!]] // for testing
    let tr = CDNresponse.data?.first?.translations ?? [] // for testing
    
    var body: some View {
        VStack {
            GeometryReader { geo in
                LazyVStack {
                    ForEach(0..<Int(mcModel.rowCount), id: \.self) { row in // create number of rows
                        HStack {
                            ForEach(0..<mcModel.columnCount, id: \.self) { column in // create 3 columns
                                if mcModel.index(row: row, column: column) < (tr.count) {
                                    VStack {
                                        MovieCellView(index: mcModel.index(row: row, column: column), tr: tr, qualities: $qualities) 
                                    }
                                }
                            }
                        }
                    }
                }.onAppear {
                    mcModel.columnCount = Int((geo.size.width / 250).rounded(.down))
                    mcModel.rowCount = Int((CGFloat(tr.count) / CGFloat(mcModel.columnCount)).rounded(.up))
                }
            }
        }
        
    }
}

struct MovieCellView: View {
    @State var index: Int

    @State var tr: [String]
    @Binding var qualities: [String : [Int : URL]]
    
    @State var showError: Bool = false
    @State var detailed: Bool = false

    var body: some View {
        Text("\(index)").foregroundColor(.red)
    }
}

Answer 2

在您的index 计算中，在ForEach 之外发生变化的唯一变量是columnCount。 row 和 column 只是循环中的索引。因此，您可以在父视图上将columnCount 声明为@State 变量，因此当它更改时，父视图将更新，因此所有单元格也将更新为新的columnCount。

@State private var columnCount: CGFloat = 0

var body: some View {
    GeometryReader { geo in
        columnCount = Int((geo.size.width / 250).rounded(.down))
        let tr = CDNresponse.data?.first?.translations ?? []
        let rowsCount = (CGFloat(tr.count) / CGFloat(columnCount)).rounded(.up)
        LazyVStack {
            ForEach(0..<Int(rowsCount), id: \.self) { row in // create number of rows
                HStack {
                    ForEach(0..<columnCount, id: \.self) { column in // create 3 columns
                        let index = row * columnCount + column
                        if index < (tr.count) {
                            VStack {
                                MovieCellView(index: index, tr: tr, qualities: $qualities)
                            }
                        }
                    }
                }
            }
        }
    }
}

Answer 3

由于没有一个答案有效，只有一个成功了一半，我自己解决了这个问题。你需要生成一个Binding，然后直接传过去

var videos: some View {
        GeometryReader { geo in
            let columnCount = Int((geo.size.width / 250).rounded(.down))
            let rowsCount = (CGFloat((CDNresponse.data?.first?.translations ?? []).count) / CGFloat(columnCount)).rounded(.up)
            LazyVStack {
                ForEach(0..<Int(rowsCount), id: \.self) { row in // create number of rows
                    HStack {
                        ForEach(0..<columnCount, id: \.self) { column in // create 3 columns
                            let index = row * columnCount + column
                            if index < ((CDNresponse.data?.first?.translations ?? []).count) {
                                MovieCellView(translation: trBinding(for: index), qualities: qualityBinding(for: (CDNresponse.data?.first?.translations ?? [])[index]))
                            }
                        }
                    }
                }
            }
        }
    }
    private func qualityBinding(for key: String) -> Binding<[Int : URL]> {
        return .init(
            get: { self.qualities[key, default: [:]] },
            set: { self.qualities[key] = $0 })
    }
    private func trBinding(for key: Int) -> Binding<String> {
        return .init(
            get: { (self.CDNresponse.data?.first?.translations ?? [])[key] },
            set: { _ in return })
    }



struct MovieCellView: View {
    @State var showError: Bool = false
    @State var detailed: Bool = false
    @Binding var translation: String
    
    @Binding var qualities: [Int : URL]
    
    var body: some View {
        ...
    }
    
}