[英]Swift - How can I save input data into Core Data?
我正在嘗試將用戶輸入存儲到我的核心數據,但出現錯誤:
我的代碼:
import UIKit
import CoreData
class AddFriendViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
@IBOutlet weak var fName: UITextField!
@IBOutlet weak var lName: UITextField!
@IBOutlet weak var mobile: UITextField!
@IBOutlet weak var gender: UIPickerView!
@IBOutlet weak var address: UITextField!
var pickerDataSource = ["Male", "Female"];
var genderPick:String = "";
//getting picker data here
@IBAction func addFriendBtn(sender: AnyObject) {
let entityDescription = NSEntityDescription.entityForName("Friends", inManagedObjectContext: managedObjectContext)
let friends = Friends(entity: entityDescription!, insertIntoManagedObjectContext: managedObjectContext)
friends.firstName = fName.text!;
friends.lastName = lName.text!;
friends.mobile = mobile.text!;
friends.gender = genderPick;
friends.address = address.text!;
var error: NSError?
managedObjectContext!.save(&error) // error occurs here
if let err = error {
showMessage("Error While Adding to Core Data")
} else {
showMessage("Save to Core Data Successfully")
}
}
func showMessage(msg: String)
{
let alert = UIAlertController(title: "Message", message: msg, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Okay", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
}
我在以下代碼行中遇到錯誤:managedObjectContext!.save(&error)。 錯誤是“無法強制打開非可選類型'NSManagedObjectContext'的值”
var theError: NSError?
do {
try managedObjectContext!.save()
} catch {
theError = error
print("Unresolved error \(theError), \(theError.userInfo)")
}
根據Apple Doc的說法,調用保存功能時需要添加錯誤處理代碼。
在Swift中處理錯誤:
在Swift中,此方法返回Void並用throws關鍵字標記,以指示在失敗的情況下拋出錯誤。
您可以在try表達式中調用此方法,並處理do語句的catch子句中的所有錯誤,如Swift編程語言(Swift 3)中的錯誤處理和結合使用Swift與Cocoa和Objective-C(Swift 3)中的錯誤處理中所述)。
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