如何从 UITableView 中获取对象 id 并根据对象 id 删除对象？答案

【问题标题】：How to grab object id from UITableView and delete object based on object id?如何从 UITableView 中获取对象 id 并根据对象 id 删除对象？
【发布时间】：2015-02-10 02:23:08
【问题描述】：

现在我遇到了这个问题，我不知道在用户从中选择后如何从 UITableView 中获取对象 id 并将其传递给另一个视图控制器，我想根据我已经获取的对象 id 删除对象从上一个。所有数据均来自user 实体。

UITableView

var myList: Array <AnyObject> = []

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

        let appDel: AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
        let context: NSManagedObjectContext = appDel.managedObjectContext!

        /* grab object id here from core data object and pass to NSUserDefault*/
        NSUserDefaults.standardUserDefaults().setObject(objectId, forKey: "userId")

        let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)

        let deleteViewController = storyBoard.instantiateViewControllerWithIdentifier("accessView") as DeleteViewController
        self.presentViewController(deleteViewController, animated:true, completion:nil)

    }

删除视图控制器

 let objectId = NSUserDefaults.standardUserDefaults().stringForKey("userId")
/* Grab object id from NSUserDefault and delete object here*/

【问题讨论】：

标签： ios uitableview swift core-data

【解决方案1】：

我已经找到答案了。

UITableView

var myList: Array <AnyObject> = []

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

        let data: NSManagedObject = myList[indexPath.row] as NSManagedObject

        let userId = data.valueForKeyPath("userId") as? String
        NSUserDefaults.standardUserDefaults().setObject(objectId, forKey: "userId")

        let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)

        let deleteViewController = storyBoard.instantiateViewControllerWithIdentifier("accessView") as DeleteViewController
        self.presentViewController(deleteViewController, animated:true, completion:nil)

    }

删除视图控制器

let userId = NSUserDefaults.standardUserDefaults().stringForKey("userId")

                    //reference to our app delegate
                    let appDel: AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
                    let context: NSManagedObjectContext = appDel.managedObjectContext!

                    let request = NSFetchRequest(entityName: "EntityOne")
                    request.includesSubentities = false
                    request.returnsObjectsAsFaults = false
                    request.predicate = NSPredicate(format: "userId = %@", userId!)
                    let items = context.executeFetchRequest(request, error: nil)!

                    for item in items {
                        context.deleteObject(item as NSManagedObject)
                    }

【讨论】：

【解决方案2】：

我通常使用两个函数来执行此操作，一个是获取特定用户，一个是删除用户。现在这些方法假设每个对象都有一个唯一的 id，所以使用下面的函数你只需调用deleteUser(fetchUser(someID))

func fetchUser(id: Int) -> User? {

    // Define fetch request/predicate
    var fetchRequest = NSFetchRequest(entityName: "User")
    let predicate = NSPredicate(format: "id == \(id)")

    // Assign fetch request properties
    fetchRequest.predicate = predicate
    fetchRequest.fetchBatchSize = 1
    fetchRequest.fetchLimit = 1

    // Handle results
    let fetchedResults = managedObjectContext?.executeFetchRequest(fetchRequest, error: nil)

    if fetchedResults?.count != 0 {

        if let fetchedUser: User = fetchedResults![0] as? User {
            return fetchedUser
        }
    }
    return nil
}

// Delete
func deleteUser(id: Int) {
    if let user = fetchEvent(id) {
        managedObjectContext?.deleteObject(user)
    }
}

【讨论】：