swift - MVC中如何使用coredata

Question

我可以在函数中使用核心数据，但我不能在 MVC 中创建，如下所示:

class addBD{
    func add(){

        let entityDescripition = NSEntityDescription.entityForName("Radar",inManagedObjectContext: managedObjectContext!)
        let task = Radar(entity: entityDescripition!, insertIntoManagedObjectContext: managedObjectContext)
        task.descricao = vlrDesc.text
        task.latitude = fieldLatitude.text
        task.longitude = fieldLongitude.text;
        task.velocidade = picker.selectedRowInComponent(0)
        managedObjectContext?.save(nil)
        
    }
}

import UIKit
import CoreData

class adicionarRadar: UIViewController, NSFetchedResultsControllerDelegate {
   
func createTask() {
    
    adic.add()
}

我有这个错误:

Use of unresolved identifier 'managedObjectContext'

Use of unresolved identifier 'vlrDesc'

...所有变量

---

class addBD{
    func add(){

        let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
        let managedContext = appDelegate.managedObjectContext!
        
        let entityDescripition = NSEntityDescription.entityForName("Radar",inManagedObjectContext: managedContext)
        let task = Radar(entity: entityDescripition!, insertIntoManagedObjectContext: managedContext)
        task.descricao = vlrDesc.text
        task.latitude = fieldLatitude.text
        task.longitude = fieldLongitude.text;
        task.velocidade = picker.selectedRowInComponent(0)
        managedContext.save(nil)
        
    }
}

import UIKit
import CoreData

class adicionarRadar: UIViewController, NSFetchedResultsControllerDelegate {

    var velocidade = ["40","50","70","90","100","120"]
    
    var latitude:String = ""
    var longitude:String = ""
    var descrip:String = ""
    var velocid:NSNumber = 0.0
    var task: Radar? = nil
    var idPicker:Int = 0
    let adic = adiciona()
    
    let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
    
    @IBOutlet weak var fieldLatitude: UITextField!
    @IBOutlet weak var fieldLongitude: UITextField!
    @IBOutlet weak var picker: UIPickerView!
    @IBOutlet weak var vlrDesc: UITextField!

    
    @IBAction func adicionar(sender: AnyObject) {
        if task != nil {
            editTask()
        } else {
            createTask()
        }
        dismissViewController()
    }

func createTask() {
    
    adic.add()
}

func editTask() {

    task?.descricao = vlrDesc.text
    task?.latitude = fieldLatitude.text
    task?.longitude = fieldLongitude.text
    task?.velocidade = picker.selectedRowInComponent(0)
    println(picker.selectedRowInComponent(0))
    managedObjectContext?.save(nil)
    }

func dismissViewController() {
    navigationController?.popViewControllerAnimated(true)
}

    func textFieldSouldReturn (textField: UITextField) -> Bool{
        textField.resignFirstResponder()
        return true
    }
    
    override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
        self.view.endEditing(true)
    }
    
    override func viewDidLoad() {

        vlrDesc.text = descrip
        fieldLatitude.text = latitude
        fieldLongitude.text=longitude
        idPicker = Int(velocid)
        picker.selectRow(idPicker, inComponent: 0, animated: true)
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }
    
    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
        return velocidade[row]
    }
    
    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return velocidade.count
    }
    
    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
        return 1
    }

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

}

Answer 1

首先，我将从这里开始:

http://www.raywenderlich.com/85578/first-core-data-app-using-swift

这应该可以帮助您入门并指导您前往需要去的地方。

对于第一个错误:Use of unresolved identifier 'managedObjectContext'，这是因为您实际上没有从 AppDelegate 中检索到此上下文

在您的 add() 函数中使用它:

let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext!

现在您可以访问整个应用程序共享的 CoreData 托管上下文。

对于第二个错误，您一定没有在代码中的某处声明或实例化这些变量。

编辑:第二个错误:

所以，问题在于函数没有对这些变量的引用。它们在不同的类中声明，因此 addBD 类无法与它们交互。

一种解决方案是向函数 func add() 添加参数，尝试将其更改为类似

func add(vlrDesc: String, etc, etc)

当您调用 add 时，将 vlrDesc 和其他变量作为参数传入。