分段选择器视图选择具有相同索引的部分中的所有行

Question

我正在尝试创建一个包含部分的PickerView

每个项目都符合“id”，我用项目的 id 标记Text（这是唯一的，我验证没有冲突）

PickerView 似乎忽略了我分配的标签，并为每个部分选择具有相同对应索引的所有行

我还尝试使用随机 UUID 标记每个项目以检查行为，它似乎继续

struct ExperimentPickerView: View {
    @StateObject var localExperiment = RunningExperiment.active
    @StateObject var experiments = RemoteExperiments.instance
    @State var picked : Int = -1
    var body: some View {
        Picker("active", selection: $picked) {
            ForEach(Array(experiments.experiments.enumerated()), id: \.offset) { i,experiment in
                Section(header: Text("\(experiment.name)")) {
                    ForEach(Array(experiment.variations.enumerated()), id: \.offset) { j,variation in
//                        Text("\(variation.name) \(variation.id)").tag(variation.id)
                        Text("\(variation.name) \(variation.id)").tag(UUID().description)
                        
                    }
                }
            }
        }.id(picked).onReceive([self.picked].publisher.first()) { (value) in
            print(value) // prints the row number and not the id of the element
            
        }
    }
}


struct Experiment : Codable, Equatable, Identifiable {
    var id: Int {
        var hasher = Hasher()
        name.hash(into: &hasher)
        variations.hash(into: &hasher)
        return hasher.finalize()
    }
    let name : String
    let variations: [Variation]
    enum CodingKeys: String, CodingKey {
        case name
        case variations
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let n = try container.decode(String.self, forKey: .name)
        name = n
        let a = try container.decode(AnyCodable.self, forKey: .variations)
        print(a)
        let b = a.value as! [[String:Any]]
        var vars = [Variation]()
        for v in b {
            if let na = v["name"], let nna = na as? String {
                vars.append(Variation(name: nna, experiment: n))
            }
        }
        variations = vars
        
        
    }
}

struct Variation: Codable, Equatable, Identifiable, Hashable {
    var id: Int {
        var hasher = Hasher()
        name.hash(into: &hasher)
        experiment.hash(into: &hasher)
        let hashValue = hasher.finalize()
        return hashValue
    }
    
    let name: String
    var experiment: String
    
    enum CodingKeys: String, CodingKey {
        case name, experiment
    }
}

Answer 1

tag 应该与selection 类型相同，因为它用于匹配选取的行。并且id 在这种情况下不应该被修改，因为它会完全重新初始化选择器。

提供的代码不可测试，因此这里只是一个解决方案演示（您的场景的简化复制）。

使用 Xcode 12.1 / iOS 14.1 测试。

struct Pair: Hashable {
    var section = ""
    var row = -1
}

struct ExperimentPickerView: View {
    var sections = ["A", "B", "C"]
    var rows = Array(0..<5)

    @State private var picked = Pair(section: "B", row: 2) // << here !! (initialised demo)

    var body: some View {
        Picker("active", selection: $picked) {
            ForEach(sections, id: \.self) { section in
                Section(header: Text("\(section)").bold()) {
                    ForEach(rows, id: \.self) { i in
                        Text("\(section) \(i)")
                           .tag(Pair(section: section, row: i))   // << match !!
                    }
                }
            }
        }.onReceive([self.picked].publisher.first()) { (value) in
            print(value)
        }
    }
}