Question

我正在尝试学习Swift，SwiftUI和Combine，并且对iOS来说是新手。最终，我希望有一个可以搜索，过滤和排序的列表。

到目前为止，当我在TextField中使用onEditingChanged时，我的过滤工作正常，但这需要按回车键。我只是想不通如何在TextField activePeople更改时如何触发filterText进行更新，以便activePeople列表在您键入时进行过滤。

当我在视图中过滤ForEach中的列表时，我已经有了一个可用的版本（请参阅注释掉的代码），但最终过滤和排序将变得更加复杂，将其置于外部似乎更有意义该视图。让我知道由于某种原因这不是正确的方法。

这是到目前为止的代码：

import Combine
import SwiftUI

class Model: ObservableObject {
    @Published var filterText: String = “”
    @Published var activePeople: [Person] = []

    private var allPeople : [Person] = [
        Person( id: 1000, name: “Alexa” ),
        Person( id: 1001, name: “Anaïs” ),
        Person( id: 1002, name: “Earl” ),
        Person( id: 1003, name: “Elba” ),
        Person( id: 1004, name: "Emil” ),
        Person( id: 1005, name: “Janeth” ),
        Person( id: 1006, name: “Joselyn” ),
        Person( id: 1007, name: “Lupita” ),
        Person( id: 1008, name: “Mellie” ),
        Person( id: 1009, name: “Vanita” ),
    ]

    init() {
        activePeople = allPeople
    }

    func filterList() {
        if ( filterText == “” ) {
            activePeople = allPeople
        } else {
            activePeople = allPeople.filter( { $0.name.localizedStandardContains( filterText ) } )
        }
    }

}

struct Person: Identifiable {
    var id: Int
    var name: String
}

import SwiftUI

struct ContentView: View {
    @EnvironmentObject private var model: Model

    var body: some View {
        VStack {
            Form {
                Section {
                    TextField(“Filter Text”, text: $model.filterText, onEditingChanged: {_ in self.model.filterList()}
                    )
                }
                Section {
                    Text( "Filtered by: \(model.filterText)” )
                    ForEach( model.activePeople ) { person in
//                        if ( self.model.filterText == “” || person.name.localizedStandardContains( self.model.filterText )) {
                            Text( person.name )
//                        }
                    }
                }
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
            .environmentObject(Model())
    }

}

Answer 1

只需在您的ContentView中应用过滤：

ForEach(model.activePeople.filter({ self.model.filterText.isEmpty ||
                                   $0.name.localizedStandardContains(self.model.filterText)})) { person in
                            Text( person.name )
                    }

Answer 2

为了观察文本字段输入的变化，可以观察模型中的变量。从视图中删除过滤逻辑可能也是一个好主意。一个示例是在模型初始化时开始观察filterText。另外，请记住保留对从sink返回的可取消对象的引用。我们所做的是每次filterText中的值发生变化（并且由于文本字段绑定而发生变化）时，我们将过滤数组并将值分配给activePeople变量

 var filterCancellable: AnyCancellable?

    init() {
        filterCancellable = $filterText.sink {[weak self] currentText in
            guard let strongSelf = self else { return } 
            strongSelf.activePeople = strongSelf.filterList(with: currentText)
        }
    }

    func filterList(with text: String) -> [Person] {
        if ( text == "" ) {
            return allPeople
        } else {
            return allPeople.filter( { $0.name.localizedStandardContains( text ) } )
        }
    }

这样您以后就可以做

var body: some View {
        VStack {
            Form {
                Section {
                    TextField("Filter Text", text: $model.filterText)
                }
                Section {
                    Text( "Filtered by: \(model.filterText)" )
                    ForEach( model.activePeople ) { person in
                        Text( person.name )
                    }
                }
            }
        }
    }

您如何更改TextField的值以触发对SwiftUI中的另一条数据的更新？

2 个答案: