取回请求返回{（//值）}而不仅仅是值

问题描述：

我有一个非常困难的时间搞清楚如何提取实体之间的关系值。我有一个Food实体和一个Meal实体。为了演示目的，我只列出了每个属性的1个属性。用于餐食的标题和用于食物的蛋白质。我的人际关系是餐饮和食物之间的关系，多对多。我想要做的是获取一份膳食并返回与该膳食相关的蛋白质值。我将最终通过日期提取膳食，然后从该膳食中提取营养信息。我发现的解决方案不仅返回了模拟器标签图片所示的值。请任何帮助将非常感激！我有一种感觉，有一种更简单的方法来做我想做的事情，但我一直在寻找几个小时，但无法弄清楚。取回请求返回{（//值）}而不仅仅是值

我尝试发布图片，但它不会让我这样我会发布我的代码，发生了什么。

ViewController.swift

import UIKit 
import CoreData 

class ViewController: UIViewController { 
    @IBOutlet weak var label: UILabel! 
override func viewDidLoad() { 
    super.viewDidLoad() 
    // Do any additional setup after loading the view, typically from a nib. 


    let appDelegate = UIApplication.shared.delegate as! AppDelegate 
    let context = appDelegate.persistentContainer.viewContext 

    //================================ 
    //CREATE MEAL AND FOOD 
    //================================ 
    let newMeal = NSEntityDescription.insertNewObject(forEntityName: "Meal", into: context) as! Meal 
    newMeal.title = "Meal 1" 

    let newFood = NSEntityDescription.insertNewObject(forEntityName: "Food", into: context) as! Food 
    newFood.protein = "20" 
    newFood.setValue(newMeal, forKey: "meal") 

    //================================ 
    //FETCH REQUEST 
    //================================ 
    let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Meal") 
    let sortDescriptor = NSSortDescriptor(key: "title", ascending: true) 
    request.sortDescriptors = [sortDescriptor] 
    request.returnsObjectsAsFaults = false 
    do { 
     //=============================== 
     //EXTRACT RELATIONSHIP DATA 
     //============================== 
     let results = try context.fetch(request) as NSArray 
     for res in results { 
      let data = res as! Meal 
      let item = data.food 
      let strs = item.value(forKey: "protein") 
      self.label.text = "\(strs)" 
     } 
    } catch { 
     print ("error") 
    } 
}

我的标签显示这...

{（）}

我需要简单地拉 '20' 出来。尝试将label.text值设置为str！字符串也不会工作。任何指导？非常感谢你

答

下面会做什么？

self.label.text = strs

不，这是行不通的跟踪时 – lilbill412

您能查看“项目”的类型？它是什么？ –

你指的是什么变量？ – lilbill412

答

我想通了.....

import UIKit 
import CoreData 

class ViewController: UIViewController { 

var item:NSSet = [] 
var strs:NSSet = [] 

@IBOutlet weak var label: UILabel! 

override func viewDidLoad() { 
    super.viewDidLoad() 
    // Do any additional setup after loading the view, typically from a nib. 


    let appDelegate = UIApplication.shared.delegate as! AppDelegate 
    let context = appDelegate.persistentContainer.viewContext 

    //================================ 
    //CREATE MEAL AND FOOD 
    //================================ 
    let newMeal = NSEntityDescription.insertNewObject(forEntityName: "Meal", into: context) as! Meal 
    newMeal.title = "Meal 1" 

    let newFood = NSEntityDescription.insertNewObject(forEntityName: "Food", into: context) as! Food 
    newFood.protein = "20" 
    newFood.setValue(newMeal, forKey: "meal") 

    //================================ 
    //FETCH REQUEST 
    //================================ 
    let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Meal") 
    let sortDescriptor = NSSortDescriptor(key: "title", ascending: true) 
    request.sortDescriptors = [sortDescriptor] 
    request.returnsObjectsAsFaults = false 
    do { 
     //=============================== 
     //EXTRACT RELATIONSHIP DATA 
     //============================== 
     let results = try context.fetch(request) as! [Meal] 
     for res in results { 

      item = res.food 

      strs = item.value(forKey: "protein") as! NSSet 
      let array = strs.allObjects 
      print(array[0]) 

      self.label.text = String(format: "%@", array[0] as! CVarArg) 
     } 
    } catch { 
     print ("error") 
    } 
} 

override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 
    // Dispose of any resources that can be recreated. 
} 


}

感谢您的帮助

取回请求返回{（//值）}而不仅仅是值

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