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SwiftData-无法转换“谓词表达式”类型的值。相等<谓词表达式。KeyPath<谓词表达式。变量<数组<Todo>。元素>

swiftdata swiftui

0

ian · 技术社区 · 11 月前

在视图中尝试初始化SwiftData查询时,我收到以下错误:

 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)
           }
    }
}

当我尝试为查询赋予值时,会出现错误 currentSection.section 如果我更换 当前章节 带有硬编码 Int 没有错误。

据我所知,这是因为我环境不会传递给 ToDoView.swift 直到车身是这样创建的 当前章节 在以下情况下不存在 init 发生。

通过我的正确方式是什么 当前章节 价值进入 init ?

1 回复 | 直到 11 月前

1

Sweeper 11 月前

我会做 TodoView 不依赖于环境对象来创建 Query .拿着 init 记下节号。

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)
            // ...
        }
    }
}

然后得到 EnvironmentObject 在父视图中:

struct TodoWrapper: View {
    @EnvironmentObject var currentSection: Section

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