I have two NSArrayControllers that use Core Data entities and I want to move objects at certain indices (via NSIndexSet) from one AC to the other. Normally this would be easy but here it's not because Core Data is under it and if I try it, it seems to remove the objects from the source AC but not adding them to the target AC. I'm using this code:
extension NSIndexSet
{
func toArray() -> [Int]
{
var indexes:[Int] = [];
self.enumerateIndexesUsingBlock
{
(index:Int, _) in
indexes.append(index);
}
return indexes;
}
}
func moveIndicesToTargetAC(indexSet:NSIndexSet)
{
let a = indexSet.toArray();
for i in a
{
var obj:NSManagedObject = sourceArrayController?.arrangedObjects.objectAtIndex(i) as! NSManagedObject;
targetArrayController?.addObject(obj);
sourceArrayController?.removeObjectAtArrangedObjectIndex(i);
}
}
What do I need to do to have Core Data regard the deletions and additions?
Thanks for hints anyone! I solved the issue by creating a new object of the target (NSManagedObject) entity and transfer all the data over to it. It was indeed an issue because the core data entities of the two ACs is different.
Related
I'm trying to use CoreData framework inside an iOS app for the first time and I have some troubles with it.
I have a kind of complex type of array, containing tuples that contains dictionaries:
let DataSet: [( Float, Float, [String : String])] = ...
I created an NSManagedObjectContext and an NSManagedObject, I added the DataSet array to the NSManagedObject, but when I try to save the 1st NSManagedObjectContext, the app is crashing.
That's not happening using normal arrays but only with more complex ones like the one above.
Is there a way to deal with that problem? Do I need to adjust my xcdatamodel?
I would appreciate any help a lot.
First you need to declare 2 separate entities. One for Floats and another for Dictionary.
Then create "One to Many" relation ship between Float entity and Dictionary. It will look like this,
Then you need to convert your tuple into these 2 entities, Like this,
dataSet.forEach{ (member) in
let tuple = Test.(context: mainContext)
tuple.first = member.0
tuple.second = member.1
let dictionary = member.2
dictionary.forEach{ (key, value) in
let dick = Dick.(context: mainContext)
dick.key = key
dick.value = value
tuple.addToContains(dick)
}
}
Finally you need to save the values.
if mainContext.hasChanges {
do {
try mainContext.save()
} catch {
print(\(error))
}
}
I have the following situation:
I have a UIViewController that has embedded two Container Views, one is hidden and one is visible. Both of those Container Views have embedded another UIViewControllers with some elements.
I want to present a data fetched from webservice on both panels, but I want to fetch the data only once, then just parse it in a specific way, based on what panel user currently sees.
I have a method that fetches data as json:
func loadInitialDataWithoutCluster() {
print("loadInitialData");
RestApiManager.sharedInstance.getRequests { json in
if let jsonData = json.array {
for requestJSON in jsonData {
dispatch_async(dispatch_get_main_queue(),{
if let request = SingleRequest.fromJSON(requestJSON){
//how can I add those single requests
// to a list/array/whatever here that will be
// accessible from both of two other panels?
}
})
}
}
}
}
and then when it fetches all the data and (somehow) assigns it to the list/array - how can I refer to it from two different panels?
This would be the solution for best programming practice. Technically you shouldn't allow any class to manipulate your data directly, instead create functions which do the work for you. I have included a function which reads and writes to an array, you can manipulate these to your needs.
class ArrayObject {
private var downloadedData = [1,2,3]
internal func readData() -> [Int] {
return downloadedData
}
internal func addData(number: Int) -> [Int] {
downloadedData.append(number)
return downloadedData
}
}
class genericControllerClass: UIViewController {
func currentData() {
let getUsers = ArrayObject().addData(15)
}
}
You can create a new file with a simple structure to store an array of the details you need, you can access this from anywhere in the project.
struct Arrays {
static var downloadedData = [TheTypeYouNeedToStore]()
}
You can add to this array once the data has been downloaded just by using Arrays.downloadedData.append(). Then anywhere else in the project this can be accessed and modified using Arrays.downloadedData[0]
I'm learning to be an iOS app developer and I want to make an app which stores core data. I know how to do it using tables but is there a way I can store data without using tables? Like I'm trying to make an app which saves about a 100 different variables but m not using tables in it. Can someone please direct me to a full tutorial of how it's done? I came across one tutorial on Ray weindervich but it was done on swift 1.2 and it didn't work for me. Thanks
Core data depends on entities, now something that might help to share (probably you knew this already) is that Core data entity is not a table it represents a thing that can be identify and quantify for example a fruit regardless what your back end is; with that been said, now I have a question, when you say table do do you mean the entities or an actual database table? If you mean entity, with Core data you can say use SQLite as backend or xml file as back end but regardless how you store the data you will need to create at least one entity.
What was suggested in the comments still using entities. So my suggestion would be just create one entity using one of this options:
1. Entity
variable1 datatype
variable2 datatype
...
...
variable n datatype
or
2. Entity
key String
Value object
With option one you will have to know all the possible variables that your application will use and one good advantage is that you won't have to do down casting neither unwrapping.
With option two you don't need to know all the possible variables and also your data can grow without changing the app, the only downside is you will have to wrap and unwrap the data from each record.
These are my suggestions for you.
Hope this help
UPDATE :
So here are the steps that I think you need to follow to achieve your request (important: this a simple sample):
Make sure your project has enable since creation Core Data.
In the Model add the Entity as the picture shows:
Then add the attributes as the picture shows:
Add the add the subclass; this part is not mandatory but makes it easy to handle each entity and its properties.
Then you should have something similar to the following code for the entity:
import Foundation
import CoreData
class Generic: NSManagedObject {
#NSManaged var key: String?
#NSManaged var value: NSObject?
}
And your view controller should have something like this in order to read and save the data:
import UIKit
import CoreData
class ViewController: UIViewController {
#IBOutlet var txtVariable: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let delegate = UIApplication.sharedApplication().delegate as! AppDelegate
let context = delegate.managedObjectContext
let request = NSFetchRequest(entityName: "Generic")
let filter = NSPredicate(format: "key = %#", "xyz")
request.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: [filter])
do {
let records = try context.executeFetchRequest(request) as! [Generic]
if (records.count>0)
{
txtVariable.text = (records[0].value as! String)
}
}
catch let error as NSError{
NSLog(error.localizedDescription)
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func btnSave_Click(sender: AnyObject) {
let delegate = UIApplication.sharedApplication().delegate as! AppDelegate
let context = delegate.managedObjectContext
let record = NSEntityDescription.insertNewObjectForEntityForName("Generic", inManagedObjectContext: context) as? Generic
record?.key = "xyz"
record?.value = txtVariable.text
do {
try context.save()
}
catch let error as NSError{
NSLog(error.localizedDescription)
}
}}
I'll make it short as possible.
I have an API request that I fetch data from (i.e. Parse).
When I'm getting the results I'm writing it to Realm and then adding them to a UICollectionView's data source.
There are requests that take a bit more time, which run asynchronous. I'm getting the needed results after the data source and collection view was already reloaded.
I'm writing the needed update from the results to my Realm database.
I have read that it's possible to use Realm's Results. But I honestly didn't understood it. I guess there is a dynamic and safe way working with collection views and Realm. Here is my approach for now.
This is how I populate the collection view's data source at the moment:
Declaration
var dataSource = [Realm_item]()
where Realm_item is a Realm Object type.
Looping and Writing
override func viewDidLoad() {
super.viewDidLoad()
for nowResult in FetchedResultsFromAPI
{
let item = Realm_item()
item.item_Title = nowResult["Title"] as! String
item.item_Price = nowResult["Price"] as! String
// Example - Will write it later after the collectionView Done - Async request
GetFileFromImageAndThanWriteRealm(x.image)
// Example - Will write it later after the collectionView Done - Async request
dataSource.append(item)
}
//After finish running over the results *Before writing the image data*
try! self.realm.write {
self.realm.add(self.dataSource)
}
myCollectionView.reloadData()
}
After I write the image to Realm to an already created "object". Will the same Realm Object (with the same primary key) automatically update over in the data source?
What is the right way to update the object from the data source after I wrote the update to same object from the Realm DB?
Update
Model class
class Realm_item: Object {
dynamic var item_ID : String!
dynamic var item_Title : String!
dynamic var item_Price : String!
dynamic var imgPath : String?
override class func primaryKey() -> String {
return "item_ID"
}
}
First I'm checking whether the "object id" exists in the Realm. If it does, I fetch the object from Realm and append it to the data source. If it doesn't exist, I create a new Realm object, write it and than appending it.
Fetching the data from Parse
This happens in the viewDidLoad method and prepares the data source:
var query = PFQuery(className:"Realm_item")
query.limit = 100
query.findObjectsInBackgroundWithBlock { (respond, error) -> Void in
if error == nil
{
for x in respond!
{
if let FetchedItem = self.realm.objectForPrimaryKey(Realm_item.self, key: x.objectId!)
{
self.dataSource.append(FetchedItem)
}
else
{
let item = Realm_item()
item.item_ID = x.objectId
item.item_Title = x["Title"] as! String
item.item_Price = x["Price"] as! String
let file = x["Images"] as! PFFile
RealmHelper().getAndSaveImageFromPFFile(file, named: x.objectId!)
self.dataSource.append(item)
}
}
try! self.realm.write {
self.realm.add(self.dataSource)
}
self.myCollectionView.reloadData()
print(respond?.count)
}
}
Thank you!
You seem to have a few questions and problems here, so I'll do my best.
I suggest you use the Results type as your data source, something like:
var dataSource: Results<Realm_item>?
Then, in your viewDidLoad():
dataSource = realm.objects(Realm_item).
Be sure to use the relevant error checking before using dataSource. We use an optional Results<Realm_item> because the Realm object you're using it from needs to be initialised first. I.e., you'll get something like "Instance member * cannot be used on type *" if you try declaring the results like let dataSource = realm.objects(Realm_item).
The Realm documentation (a very well-written and useful reference to have when you're using Realm as beginner like myself), has this to say about Results...
Results are live, auto-updating views into the underlying data, which means results never have to be re-fetched. Modifying objects that affect the query will be reflected in the results immediately.
Your mileage may vary depending on how you have everything set up. You could try posting your Realm models and Parse-related code for review and comment.
Your last question:
What is the right way to update the "object" from the Data Source after i wrote the update to same object from the Realm DB?
I gather you're asking the best way to update your UI (CollectionView) when the underlying data has been updated? If so...
You can subscribe to Realm notifications to know when Realm data is updated, indicating when your app’s UI should be refreshed for example, without having to re-fetch your Results.
I'm trying to make an iOS 8 App with Swift and i need to download data from JSON and save it , but i don't understand Core Data mechanism. (I'm coming from Android with ORM Lite and Windows Phone with sqlite-net).
I'm trying to make two tasks, "GetAllNewsTask" returning all News from database , and "UpdateAllNewsTask" downloading JSON and parsing it, save to database and return all News.
The function getEntitiesFromJson transform parsed JSON string to entity object
class func getEntitiesFromJson(json: JSONValue) -> [NewsEntity]?{
var rList : [NewsEntity] = []
var array = json.array
var countItr = array?.count ?? 0
if(array == nil){
return nil
}
if(countItr > 0){
for index in 0...countItr-1{
var news = NewsEntity()
var jsonVal = array?[index]
news.id = jsonVal?["id"].integer ?? 0
........
rList.append(news)
}
}
return rList
}
GetAllNewsTask (newsDao.findAll() currently return an harcoded empty array, i didn't found how to select all NewsEntity synchronously)
class GetAllNewsTask:NSOperation {
var result : Array<News>?
override func main() -> (){
result = executeSync()
}
func executeSync() -> Array<News>? {
let newsDao = NewsDAO()
let entities = newsDao.findAll()
return NewsModel.getVOsFromEntities(entities)
}
UpdateAllNewsTask
class UpdateAllNewsTask:NSOperation {
var result : Array<News>?
override func main() -> (){
result = executeSync()
}
func executeSync() -> Array<News>? {
let response = JsonServices.getAllNews()
var managedObjectContext = (UIApplication.sharedApplication().delegate as AppDelegate).managedObjectContext!
var entityDescription = NSEntityDescription.entityForName("NewsEntity", inManagedObjectContext: managedObjectContext)
var entities = NewsModel.getEntitiesFromJson(response)
//TODO insert new, update existing and remove old
return GetAllNewsTask().executeSync()
}
I'm trying to add or update all NewsEntity and delete old, in Java i used List.removeAll(Collection<T>) but i can't found how to do this in Swift.
I got an exception when i override equals and hashcode in NewsEntity class.
Before continuing, is it the correct way to do this ?
If yes there is any good tutorial which demonstrate how to do this?
If no what is the correct way ?
Typically Core Data transactions should always be performed on the object's Managed Object Context thread. For this reason you will see the performBlock and performBlockAndWait calls in NSManagedObjectContext.
Since you are using the main thread you are technically synchronous assuming you are making those update calls on the main thread. If you are not then I would suggest wrapping your synch call into a performBlockAndWait call.
That being said, you should leverage Apple's Documentation on the subject as they explain how you can implement multithreaded core data. You should always perform your server related updates on a background thread.
If you want to implement a removeAll feature you will need to manually fetch all the objects you want to remove and call context.deleteObject(managedObject). Alternatively if you want something more powerful that should enforce cascade deletion, you can set this in your model editor when you select the relationship. The following Delete Rules are available:
Nullify
Cascade
No Action
Deny
Finally, you might find this post useful in explaining some of the commonly used Core Data stack setups and the various performance of each.
Welcome to iOS and good luck:)
EDIT
As an aside you might find Ray Wenderlich provides some great Core Data Tutorials