如何在 CoreData Swift 3 中删除所有实体对象答案

【问题标题】：How To Delete all Entity Objects in CoreData Swift 3如何在 CoreData Swift 3 中删除所有实体对象
【发布时间】：2017-04-24 20:42:02
【问题描述】：

所以我有这段代码可以正常工作，但我想要一个更好的代码。

func deleteCoreDataObjects() {
    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    //where groupData is an Array of an Entity
    for i in 0..<self.groupData.count {
        context.delete(groupData[i])
    }


    (UIApplication.shared.delegate as! AppDelegate).saveContext()

}

目前我正在通过for循环一一删除对象。

【问题讨论】：

标签： swift xcode core-data swift3 xcode8

【解决方案1】：

你可以试试这个：

func deleteAllData(entity: String)
{
    let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let managedContext = appDelegate.managedObjectContext
    let fetchRequest = NSFetchRequest(entityName: entity)
    fetchRequest.returnsObjectsAsFaults = false

    do 
    {
        let results = try managedContext.executeFetchRequest(fetchRequest)
        for managedObject in results
        {
            let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
            managedContext.deleteObject(managedObjectData)
        }
    } catch let error as NSError {
        print("Detele all data in \(entity) error : \(error) \(error.userInfo)")
    }
}

用法：

self.deleteAllData("your_entityName")

已经出现在：https://stackoverflow.com/a/33931528/2894160

【讨论】：

【解决方案2】：

这是从 Core Data 中删除记录的代码： //从本地数据库中删除用户信息

func deleteUserInfo()  {

    let context = appdelegate.managedObjectContext
    let coord   = appdelegate.persistentStoreCoordinator

    let fetchRequest = NSFetchRequest(entityName: "User")
    if #available(iOS 9.0, *) {
        let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
        //let predicate = NSPredicate(format: "id == %@", key)
        //fetchRequest.predicate = predicate
        do {
            try coord.executeRequest(deleteRequest, withContext: context)
        }
        catch let error as NSError {
            //Error handling
        }
        catch {}
    } else {
        // Fallback on earlier versions

        do {
        let users: NSArray = try appdelegate.managedObjectContext.executeFetchRequest(fetchRequest)

        for user in users {
            appdelegate.managedObjectContext.delete(user)
        }

        try appdelegate.managedObjectContext.save()

        } catch let error as NSError {
            //Error handling
        }
        catch {}
    }
}

【讨论】：

【解决方案3】：

最好是删除持久性存储，然后添加新的而不是循环每个实体（如果您想从 coredata 中删除 所有实体）。

func deletePersistentStoreCoordinator () {

    do {
        let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("YourDatabaseName.sqlite")
        try self.persistentStoreCoordinator.destroyPersistentStoreAtURL(url, withType: NSSQLiteStoreType, options: nil)
        try self.persistentStoreCoordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
    }
    catch{

    }
}

【讨论】：