Question

我正在尝试学习如何从博客中读取数据并将其保存到核心数据，但保存不按预期工作。有4个博客条目，我希望在核心数据中有4个不同的条目。请参阅下面的代码，让我知道我哪里出错：

 let task = session.dataTaskWithURL(url!, completionHandler:{(data , response, error) -> Void in
        if (error != nil){
            println(error)
        }else{
            var jsonResult:NSDictionary = NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers, error: nil) as NSDictionary
            var managedObjectContext = (UIApplication.sharedApplication().delegate as AppDelegate).managedObjectContext!
            let newBlog = NSEntityDescription.insertNewObjectForEntityForName("BlogDetails",inManagedObjectContext:managedObjectContext) as NSManagedObject
            var dateFormater = NSDateFormatter()
            dateFormater.dateFormat = "yyyy-MM-dd HH:mm:ss" //"yyyy-MM-dd"
            var readRequest = NSFetchRequest(entityName: "BlogDetails")
            for var i = 0; i < ((jsonResult["items"] as? NSArray)?.count)!; i++ {
                var item = jsonResult["items"]![i] as NSDictionary
                var blogAuthorDirectory = item["author"]! as NSDictionary
                var blogAuthor = blogAuthorDirectory["displayName"] as NSString
                var blogAuthorImageDirectory = blogAuthorDirectory["image"] as NSDictionary
                // concatenate String
                var blogAuthorImage =  blogAuthorImageDirectory["url"] as NSString
                var blogAuthorImageUrl = ("https:" + blogAuthorImage)
                var title = item["title"] as String
                // convert date from String
                var publishedDate:NSDate = dateFormater.dateFromString(stringTmp as NSString)!
                // read content
                var content = item["content"] as? NSString
                // Write it to core data
                newBlog.setValue(blogAuthorImageUrl, forKey: "image")
                newBlog.setValue(blogAuthor, forKey: "author")
                newBlog.setValue(title, forKey: "title")
                newBlog.setValue(publishedDate, forKey: "publisheddate")
                managedObjectContext.save(nil)
                var results = managedObjectContext.executeFetchRequest(readRequest, error: nil)
                println(results)
            }
        }
    })
    task.resume()

以下是上次迭代中的结果条目：它只有3个字典计数，其中前2个计数中的值都是nil。怎么生成？ 2.对于每次迭代，它会覆盖最后一次计数中的值，并且不会附加它。

感谢您的帮助。

Answer 1

如果要将对象附加到CoreData，则需要在调用managedContext.save(nil)方法之前执行insertIntoManagedObjectContext。

然而，你的

let newBlog = NSEntityDescription.insertNewObjectForEntityForName("BlogDetails",inManagedObjectContext:managedObjectContext) as NSManagedObject

在for循环之外声明，因此可能在每次迭代后都没有创建新博客。

问题：将Json数据保存到Core Data

1 个答案: