SwiftUI Picker 从 CoreData 返回空字符串

Posted 2023-02-24

【中文标题】SwiftUI Picker 从 CoreData 返回空字符串

【英文标题】：SwiftUI Picker return empty string from CoreData

【发布时间】：2020-08-06 09:15:24

【问题描述】：

如何改进？当我使用ForEach（CoreData 实体）时，选择器返回空字符串。如果我使用 testing[String] 一切正常

import SwiftUI

struct AddTask: View 
    @Environment(\.managedObjectContext) var moc
    @FetchRequest(entity: Goal.entity(), sortDescriptors: []) var goals: FetchedResults<Goal>
    
    @State private var taskName: String = ""
    @State private var originGoal = ""
    private let testGoal = ["Alpha", "Bravo", "Charlie"]
    
    var body: some View 
        NavigationView 
            Form 
                Section
                    TextField("Enter Task Name", text: $taskName)
                
                Section 
                    Picker(selection: $originGoal, label: Text("Choose Goal")) 
                        ForEach(goals, id: \.self)  goal in
                            Text(goal.wrappedName)
                        
                    
                
            
        
        
        Button("Add") 
            let task1 = Task(context: self.moc)
            task1.name = taskName
            task1.origin = Goal(context: self.moc)
            task1.origin?.name = originGoal
            
            try? self.moc.save()
        
    

或者也许 SwiftUI Picker 有不错的替代品？

【问题讨论】：

Picker return empty String 是什么意思？

选择器不要从目标列表中选择任何变体，显示，但不要选择

【参考方案1】：

selection 和id 应该是Picker 中的相同类型，所以试试（无法测试您的代码）：

Section 
    Picker(selection: $originGoal, label: Text("Choose Goal")) 
        ForEach(goals, id: \.wrappedName)  goal in
            Text(goal.wrappedName)
        
    

有时tag 也有效（但并非总是如此），所以也试试

Section 
    Picker(selection: $originGoal, label: Text("Choose Goal")) 
        ForEach(goals, id: \.self)  goal in
            Text(goal.wrappedName).tag(goal.wrappedName)