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ian
Asked: 2024-08-31 09:35:40 +0800 CST

SwiftData - 无法转换类型为“PredicateExpressions.Equal <PredicateExpressions.KeyPath <PredicateExpressions.Variable <Array <Todo>.Element>”的值

  • 772

尝试在视图中初始化 SwiftData 查询时收到以下错误：

 Error: Cannot convert value of type 'PredicateExpressions.Equal<PredicateExpressions.KeyPath
<PredicateExpressions.Variable<Array<Todo>.Element>, Int>, PredicateExpressions.KeyPath<PredicateExpressions.Value<Section>, 
Int>>'(aka'PredicateExpressions.Equal<PredicateExpressions.
KeyPath<PredicateExpressions.Variable<Todo>, Int>, PredicateExpressions.KeyPath<PredicateExpressions.Value<Section>, 
Int>>') to closure result type 'any StandardPredicateExpression<Bool>'

TodoView.swift

import SwiftUI
import SwiftData

struct TodoView: View {
    
    @Query var todos: [Todo]
    
    @EnvironmentObject var currentSection: Section
    
    @Environment(\.modelContext) var modelContext
    
    var DWMY = ["D","W","M","Y"]
    
    var body: some View {
        List {
            ForEach(todos) { todo in
                HStack {
                    if todo.completed == false {
                        Text("[ ]")
                    } else {
                        Text("[X]")
                    }
                    Text(todo.name)
                    Text(DWMY[todo.section])
                }
            }
            .onDelete(perform: deleteToDo)
        }
        .navigationBarTitleDisplayMode(.inline)
    }
    
    init(todoSection: Section) {
        _todos = Query(filter: #Predicate { todo in
            todo.section == currentSection.section
        })
    }
    
    func deleteToDo(at offsets: IndexSet ) {
           for offset in offsets {
               let todo = todos[offset]
               modelContext.delete(todo)
           }
    }
}

当我尝试为查询提供值时会发生错误，currentSection.section如果我currentSection.section用硬编码的Int替换则不会出现任何错误。

据我所知，发生这种情况是因为我的环境ToDoView.swift直到Body创建后才被传递下去，因此发生currentSection.section时不存在init。

currentSection.section将我的价值传递到的正确方法是什么init？

swiftui

1 个回答

  1. Best Answer

    我将使TodoView不依赖于环境对象来创建Query。 将init纳入部分编号。

    struct TodoView: View {
    @Query var todos: [Todo]

    // you could still have the EnvironmentObject here for other purposes, just not for creating the query
    // @EnvironmentObject var currentSection: Section
    
    init(sectionNumber: Int) {
        _todos = Query(filter: #Predicate { todo in
                    todo.section == sectionNumber
                })
    }
    
    var body: some View {
        List(todos) { todo in
            Text(todo.name)
            // ...
        }
    }
}

    EnvironmentObject然后在父视图中获取：

    struct TodoWrapper: View {
    @EnvironmentObject var currentSection: Section

    var body: some View {
        TodoView(sectionNumber: currentSection.section)
    }
}
    • 1

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