Question

我想更新核心数据记录。首先，我搜索了该记录是否存在。如果它存在，则需要更新，如果没有创建新记录。
最后应返回Post实例我不知道如何使用setValue更新它以及如何返回post实例。因为我用这行代码初始化了post实例：

post = NSEntityDescription.insertNewObjectForEntityForName()

我不知道如何更新这个。

class Post: NSManagedObject {

}
    var post: Post!


 private static func postFromJSONObject(json: [String:AnyObject], inContext context: NSManagedObjectContext) -> Post? {

   .
   .
   .
    let coreDataStack = CoreDataStack(modelName: "ProjectPart1")
    let mainQueueContext = coreDataStack.mainQueueContext

    let fetchRequest = NSFetchRequest(entityName: "Post")
    fetchRequest.predicate = NSPredicate(format: "id = %@", "\(postID)")
    do {
        let foundRecordsArray = try! mainQueueContext.executeFetchRequest(fetchRequest) as! [Post]

        if foundRecordsArray.count > 0 {
            //here is where I should update Core Data!


        } else{
            context.performBlockAndWait() {
                post = NSEntityDescription.insertNewObjectForEntityForName("Post", inManagedObjectContext: context) as! Post
                post.title = postTitle
                post.body = postBody
                post.id = postID
                post.userId = postUserID
            }
        }
    } catch {
        print("error")
    }
    return post
}

我试过这个，但它也没有用。

  if foundRecordsArray.count > 0 {
                var res = foundRecordsArray[0] as NSManagedObject
                res.setValue(postID, forKey: "id")
                res.setValue(postUserID, forKey: "userId")
                res.setValue(postTitle, forKey: "title")
                res.setValue(postBody, forKey: "body")

                post = res as! Post

            }

错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[ProjectPart1.Post title]: unrecognized selector sent to instance 0x7f8e5180e0b0'

Answer 1

    fetchRequest.fetchLimit = 1
    var post:Post!
   if let foundRecordsArray = try? mainQueueContext.executeFetchRequest(fetchRequest), foundRecordsArray.count > 0
      {
               post = foundRecordsArray[0]

      } else{            // Create new

         post = NSEntityDescription.insertNewObjectForEntityForName("Post", inManagedObjectContext: context) as! Post               
     }

    post.title = postTitle
    post.body = postBody
    post.id = postID
    post.userId = postUserID

使用Swift更新Core Data对象

1 个答案: