如何在Xcode 8中使用CoreData？

Question

我正在尝试使用CoreData,但是当我将它添加到我的项目中时,我只获得了两个新方法:

- (NSPersistentContainer *)persistentContainer

和

- (void)saveContext

现在我无法使用旧的方法CoreData,我找不到任何有这些新方法和Objective-C的教程.如何CoreData使用persistentContainerObjective-c在Xcode 8中保存和获取数据？

Answer 1

您可以获取上下文 -

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

或者如在Objective-C中那样

NSManagedObjectContext *context = ((AppDelegate*)[[UIApplication sharedApplication] delegate]).persistentContainer.viewContext;

并获取数据 - 如

var resultArray  = try self.context.fetch(EntityName.fetchRequest())

或者如在Objective-C中那样

NSFetchRequest<EntityName *> *fetchRequest = [EntityName fetchRequest];
NSError *error ;
NSArray *resultArray= [context executeFetchRequest:fetchRequest error:&error];

并通过排序获取数据 -

var resultArray = [EntityName]()
do {
        let request : NSFetchRequest<EntityName> = EntityName.fetchRequest()
        let sortDescriptor = NSSortDescriptor(key: "somekey", ascending: true)
        let sortDescriptors = [sortDescriptor]
        request.sortDescriptors = sortDescriptors
        resultArray = try self.context.fetch(request)
} catch {
        print("Error")
}

或者如在Objective-C中那样

NSFetchRequest<EntityName *> *fetchRequest = [EntityName fetchRequest];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"someKey" ascending:YES];
fetchRequest.sortDescriptors = @[sortDescriptor];
NSError *error ;
NSArray *resultArray= [context executeFetchRequest:fetchRequest error:&error];

并添加像 -

let entityNameObj = EntityName(context: context)
entityNameObj.title = "title"

或者如在Objective-C中那样

NSManagedObject *entityNameObj = [NSEntityDescription insertNewObjectForEntityForName:@"EntityName" inManagedObjectContext:context];
[entityNameObj setValue:@"someValue" forKey:@"someKey"];

并保存上下文,如 -

do {
     try self.context.save()
} catch _ as NSError {
     print("Error")
}

或者如在Objective-C中那样

[((AppDelegate*)[[UIApplication sharedApplication] delegate]) saveContext];