從CoreData模塊獲取數據

我正在Swift 3.0中進行項目工作，並且我有一個CoreData模塊，它具有String類型的五個屬性，並且NSManageObject的名稱爲MP3Details。他們是，持續時間，trackID,trackName,trackURL。從CoreData模塊獲取數據

要求是，一旦我通過trackID我需要檢索與該ID相關的元素。例如，一旦我通過trackID，我應該獲得屬於該曲目ID的曲目持續時間，trackName等。

截至目前我所得到的是一個空陣列。部分完成的代碼，我通過trackID並獲取屬於該ID的信息，如下所示。我在這裏錯過了什麼？

方法，其中，我通過trackID

if let arr = StorageManager.getTrackId(playlistName: playlistName) { 
    for object in arr { 
     let trackId = object.trackID 
     print(trackId ?? "ID") 

     if let detailsArr = StorageManager.getTrackDetails(trackId: trackId) { 
      print("CoreDataItemArray :", detailsArr) 

     } 
    }

方法我是否請求詳細信息從CoreData

public static func getTrackDetails(trackId:String?) -> [MP3Details]?{ 
    let appDelegate = UIApplication.shared.delegate as! AppDelegate; 
    let context = appDelegate.persistentContainer.viewContext; 

    let request = NSFetchRequest<NSFetchRequestResult>(entityName: MP3_DETAILS_ENTITY) 
    if(trackId != nil){ 
     request.predicate = NSPredicate(format:"trackID = %@", trackId!) 
    } 
    request.returnsObjectsAsFaults = false 

    do{ 
     let results = try context.fetch(request) 
     print("Result : ",results) 
     if(results.count > 0){ 

      return results as? [MP3Details] 
     }else{ 
      print("No Mp3 results for the track ID") 
     } 

    }catch{ 
     print("Error in fetching items") 
    } 
    return nil; 
}

來源

2017-05-09 danu

不，您不能使用上面的代碼swift 3.0訪問核心數據。核心數據的訪問發生了迅速變化。您可以直接訪問核心數據persistentContainer。 – phani

代碼片段將非常感激，因爲事情是當我通過一個nill值，而不是trackID我得到Mp3Details – danu

到目前爲止，我沒有在迅速工作。但我有這個代碼。等待我會檢查它。 – phani

FUNC loadData（） - >空隙{

guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { 
     return 
    } 

    let managedObjContext = appDelegate.persistentContainer.viewContext 
    let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "Person") 
    do { 
     names = try managedObjContext.fetch(fetchRequest) 
    } catch let error as NSError { 
     print("Error while fetching the data:: ",error.description) 
    } 

} 

@IBAction func addNewName(_ sender: Any) { 
    let alert = UIAlertController(title: "Add Name", message: "Add new name:", preferredStyle: UIAlertControllerStyle.alert) 
    let alertAction = UIAlertAction(title: "Add", style: UIAlertActionStyle.default) { action in 

     guard let textField = alert.textFields?.first , 
      let nameToSave = textField.text else{ 
       return 
     } 
     print("nameToSave::: ",nameToSave) 
     self.save(name:nameToSave) 
     self.hitListTableView.reloadData() 
    } 
    alert.addTextField() 

    let alertCancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel, handler: nil) 

    alert.addAction(alertAction) 
    alert.addAction(alertCancelAction) 

    self.present(alert, animated: true, completion: nil) 

} 

func save(name:String) -> Void { 

    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { 
     return 
    } 
    let managedContext = appDelegate.persistentContainer.viewContext 
    let entity = NSEntityDescription.entity(forEntityName: "Person", in: managedContext) 
    let person = NSManagedObject(entity: entity!, insertInto: managedContext) 
    person.setValue(name, forKey: "name") 

    do { 
     try managedContext.save() 
     names.append(person) 
    } catch let error as NSError { 
     print("Error while saving the data: ",error.localizedDescription) 
    } 
}

來源

2017-05-09 04:21:17 phani

謂詞在哪裏？這不符合我的要求 – danu

好的。我會再次檢查代碼。 2分鐘 – phani

Sry yar。在我的mac我有代碼。但在谷歌驅動器代碼丟失。 – phani

嘗試更換謂詞符合：

request.predicate = NSPredicate(format:"%K == %@", "trackID", trackId!)

來源

2017-05-09 07:55:43 carlito

從CoreData模塊獲取數據

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