Issue: Saving Json data to Core Data - swift

Question

I am trying to learn how to read data from a blog and save it to core data but the save is not working as intended. There are 4 blog entries and I expect to have 4 different entries in core data. Please see the code below and let me know where i went wrong:
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()
following are the entries in result in the last iteration:
1. It only has 3 dictionary counts out of which values in first 2 count has all items as nil. how is that being generated?
2. With every iteration, it overwrites value in last count and doesn't append it.
Thanks for your help.

Answer 1

If you want to append objects to your CoreData, you need to do insertIntoManagedObjectContext before you call the managedContext.save(nil) method.
However, your
let newBlog = NSEntityDescription.insertNewObjectForEntityForName("BlogDetails",inManagedObjectContext:managedObjectContext) as NSManagedObject
is declared outside of your for loop, so probably no new blog created after each iteration.