I have a Swift app that uses CoreData. I created List entity with class MyAppTarget.List. Everything is configured properly in .xcdatamodeld file. In order to fetch my entities from persistent store, I am using NSFetchedResultsController:
let fetchRequest = NSFetchRequest()
fetchRequest.entity = NSEntityDescription.entityForName("List", inManagedObjectContext: managedObjectContext)
fetchRequest.sortDescriptors = [ NSSortDescriptor(key: "name", ascending: true) ]
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: managedObjectContext, sectionNameKeyPath: nil, cacheName: "ListFetchedResultsControllerCache")
and it works like expected, returning array of MyAppTarget.List objects when fetching.
However, I would like to use it inside another target, for unit testing. I added List class to MyUnitTestTarget, so I can access it inside the unit test target. The problem is that the fetched results controller returns MyAppTarget.List objects, not the MyUnitTestTarget.List objects. In order to make the List entity testable, I have to make it public along with all methods that I need to use and I would like to avoid this.
I tried to change the managedObjectClassName property on NSEntityDescription:
fetchRequest.entity.managedObjectClassName = "MyUnitTestTarget.List"
but it generates exception:
failed: caught "NSInternalInconsistencyException", "Can't modify an immutable model."
The documentation states that
[...] once a description is used (when the managed object model to which it belongs is associated with a persistent store coordinator), it must not (indeed cannot) be changed. [...] If you need to modify a model that is in use, create a copy, modify the copy, and then discard the objects with the old model.
Unfortunately, I don't know how to implement this flow. I wonder if there is a way to change the managed object class name in runtime, before fetching the entities with NSFetchedResultsController?
It occurs that solution to my problem was pretty simple. In order to make it working, I had to create a copy of managedObjectModel, edit its entities and create NSPersistentStoreCoordinator with the new model. Changing the managedObjectClassName property on NSEntityDescription instance is possible only before model to which it belongs is associated with NSPersistentStoreCoordinator.
let testManagedObjectModel = managedObjectModel.copy() as NSManagedObjectModel
for entity in testManagedObjectModel.entities as [NSEntityDescription] {
if entity.name == "List" {
entity.managedObjectClassName = "CheckListsTests.List"
}
}
This also solves my other problem with unit testing CoreData model entities in Swift.
You can dynamically alter the class name of the NSManagedObject subclass with something like:
let managedObjectModel = NSManagedObjectModel.mergedModelFromBundles([NSBundle.mainBundle()])!
// Check if it is within the test environment
let environment = NSProcessInfo.processInfo().environment as! [String : AnyObject]
let isTestEnvironment = (environment["XCInjectBundle"] as? String)?.pathExtension == "xctest"
// Create the module name based on product name
let productName:String = NSBundle.mainBundle().infoDictionary?["CFBundleName"] as! String
let moduleName = (isTestEnvironment) ? productName + "Tests" : productName
let newManagedObjectModel:NSManagedObjectModel = managedObjectModel.copy() as! NSManagedObjectModel
for entity in newManagedObjectModel.entities as! [NSEntityDescription] {
entity.managedObjectClassName = "\(moduleName).\(entity.name!)"
}
Related
I have a one-to-many relationship in core data of plan -> recipe. plan.recipes is of type NSSet?, so I have created custom NSManagedObject classes with computed properties to convert these into arrays, adding an extra property recipesArray:
public var recipesArray: [Recipe] {
let set = recipes as? Set<Recipe> ?? []
return set.sorted {
$0.wrappedName < $1.wrappedName
}
}
I then display this list in a View using a ForEach, using the recipesArray property. A subview of this view calls plan.addToRecipes(recipe: Recipe), to add a new object to the relationship. I then save.
The issue is, the ForEach in the parent view does not react to this addition. If I refresh the view by navigating away, then the new recipe is shown, but the View is not automatically updated when the new recipe is added.
Does anyone know how to do this? Should I be using the original recipes property instead of this custom array one?
You need to make another FetchRequest for Recipes using a predicate that equals a given plan, e.g. something like this:
struct RecipesView: View {
var fetchRequest: FetchRequest<Recipe>
var recipes: FetchedResults<Recipe> { fetchRequest.wrappedValue }
init(plan: Plan) {
let sortDescriptors = ...
let predicate = NSPredicate(format: "plan = %#", plan)
fetchRequest = FetchRequest(sortDescriptors: sortDescriptors, predicate: predicate, animation: .default)
}
var body: some View {
ForEach(recipes) { recipe in
RecipeView(recipe: recipe) // it's important to not access recipe's properties (firing a fault) until inside a sub-view's body.
}
}
}
Note: There is currently a bug in FetchRequest that results in body always invoked even when this View is init with the same plan and thus same FetchRequest. This is because the FetchRequest struct inits a new object inside it every time, causing it and consequently this View to appear as changed to SwiftUI. I reported this bug so hopefully they fix it. You could workaround it in the meantime with a wrapper View that takes the plan as a let so body won't be called.
i know that this has been asked a couple of times but the usual solution does not seem to work for me. I created a CoreData entity and a subclass for it using <ProjectName>.<SubclassName> syntax as class name. Creating a new object like this:
let object = NSEntityDescription.insertNewObjectForEntityForName("User", inManagedObjectContext: CoreDataManager.sharedInstance.managedObjectContext) as User
println("-->\(object)<--")
object.setValue(12, forKey: "userID")
object.setValue("username", forKey: "username")
the console output:
although the object does not get printed in the console it seems to have been in some way created and setting a value on that object refers to a Core Data Object
when i use it without a subclass it works as expected (setting Class name back to default):
let object = NSEntityDescription.insertNewObjectForEntityForName("User", inManagedObjectContext: CoreDataManager.sharedInstance.managedObjectContext) as NSManagedObject
println("-->\(object)<--")
output:
Here's my subclass declaration:
import Foundation
import CoreData
class User: NSManagedObject {
#NSManaged var userID: NSNumber
#NSManaged var username: String
}
and here's the core data model form:
What's wrong with the code? Or do i miss anything?
For printing out the value of an NSManagedObject, do not use:
println(...)
But rather use:
NSLog(...)
Please find an example of using NSLog and an NSManagedObject below:
/**
* Called when the user clicks on the save button.
*/
#IBAction func saveTapped(sender: AnyObject) {
// Reference to our app delegate
let appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
// Reference MOC
let context: NSManagedObjectContext = appDel.managedObjectContext!
let en = NSEntityDescription.entityForName("List", inManagedObjectContext: context)
// Create instance of put data model and initialize
var newItem: List = List(entity: en!, insertIntoManagedObjectContext: context)
// Map our properties
newItem.item = textFieldItemName.text
newItem.quantity = textFieldQt.text
newItem.info = textFieldMoreInfo.text
// Save our context
var error: NSError? = nil;
if (context.hasChanges) {
if (!context.save(&error)) { // save failed
println("Save Failed: \(error!.localizedDescription)")
} else {
println("Save Succeeded")
}
}
NSLog("newItem: %#", newItem)
// Navigate back to root ViewController
self.navigationController?.popToRootViewControllerAnimated(true)
}
Note: I do not know the exact reason (bug, or implementation maybe ...) but it turns out that it does not print out a value when we use println(...) function, instead of that it returns an empty String.
Consequently I recommend to all of you guys to use NSLog(...) function instead of println(...) when you want to print out the value of an NSManagedObject.
If you print the expression CoreDataManager.sharedInstance.managedObjectContext twice, do you get a different pointer each time?
It sounds like the managed object context is getting deallocated right after you use it, which indicates that your CoreDataManager.sharedInstance.managedObjectContext property is returning a new managed object context every time, not the same one, or your sharedInstance property is returning a new instance every time.
A managed object's in-memory state is stored as a weak reference to a managed object context. When the context drops out from underneath you (e.g. it's no longer referenced and so is deallocated), your managed object's storage disappears.
A few good indicators that this is happening:
You haven't saved your managed object context yet but a newly created managed object prints as fault
You get weird errors when you try to set a property
You get weird errors when you try to retrieve a property you just set
Include the following at the top of your .swift file
import CoreData
The reason for not working is it doesn't know which library to reference.
Hope it helps
try creating it with this method :
let entityDescripition = NSEntityDescription.entityForName(“User”, inManagedObjectContext: managedObjectContext)
let user = User(entity: entityDescripition, insertIntoManagedObjectContext: managedObjectContext)
I have a very simple UITableView that loads core data records using a NSFetchedResultsController. I have re-written the Objective-C code to Swift. I seem to have an issue when running the Swift code on an iOS 7 simulator but ok on iOS 8. As far as I know Swift is supposed to be backward compatible for iOS 7.
The error I get when running iOS 7 but not 8 is:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'NSFetchRequest could not locate an NSEntityDescription for entity name 'Category''
For some reason when executing the NSFetchRequest it doesn't like my core data entity Category on iOS 7 but fine on iOS 8, any ideas?
Relevant code:
class CategoriesListTableViewController : CoreDataTableViewController, AddEditCategoryTableViewControllerDelegate {
let kCategoryEntityID = "Category"
let kCategoryCellID = "Category Cell"
let kCategoryEntityParentAttributeID = "parent"
let kCategoryEntityNameAttributeID = "name"
let kCategoriesCacheID = "Categories"
let kAddCategorySegue = "Add Category"
let kEditCategorySegue = "Edit Category"
var moc = NSManagedObjectContext()
override func viewDidLoad() {
super.viewDidLoad()
let app = UIApplication.sharedApplication().delegate as AppDelegate
moc = app.cdh().context
//debugcode
let mom = moc.persistentStoreCoordinator.managedObjectModel
let entities = mom.entitiesByName
let entityNames = entities.description
println("All loaded entities are: \(entityNames)")
self.setupFetchedResultsController()
}
func setupFetchedResultsController() // attaches an NSFetchRequest to this UITableViewController
{
let request = NSFetchRequest(entityName: kCategoryEntityID)
let sortParent = NSSortDescriptor(key: kCategoryEntityParentAttributeID, ascending: true)
let sortName = NSSortDescriptor(key: kCategoryEntityNameAttributeID, ascending: true)
let sortDescriptors = [sortParent, sortName]
request.sortDescriptors = sortDescriptors
self.fetchedResultsController = NSFetchedResultsController(fetchRequest: request, managedObjectContext: moc, sectionNameKeyPath: kCategoryEntityParentAttributeID, cacheName: kCategoriesCacheID)
}
It seems that you might not be creating your managed object context correctly. The fetch request created with an entity name string is not "complete" until it becomes associated with the actual managed object context. The managed object context in turn associates it with the managed object model which contains the necessary entity descriptions.
In this case this should happen during the initialization of the fetched results controller. Check if the correct managed object context is loaded as expected when you create the FRC.
As your different results appear in iOS7 and 8 respectively, consider deleting the app completely from the simulator first. Also, try to clean the project before building again.
I'm trying to implement a getter on one of my db classes. But when I execute the following line of code, where "obj" is an NSManagedObject:
return [obj valueForKey:#"activationData"];
I get the following NSUnknownKeyException:
'[ valueForUndefinedKey:]: the entity Blueprint is not key value coding-compliant for the key "activationData".'
I just recently added a String attribute named "activationData" to my "Blueprint" entity using Xcode. But when I run the app the NSManagedObject that represents Blueprint entities does not include the new "activationData" attribute, which apparently is the cause of the crash.
The NSManagedObject looks like this, but I expected it to show the new Attribute along with the createDate, name and order attributes:
<NSManagedObject: 0x5138c90> (entity: Blueprint; id: 0x513a2e0 <x-coredata://8C586BB8-B9E7-4FD7-84CB-5CE66FB221E6/Blueprint/p2> ; data: {
createDate = "2012-02-21 15:49:00 +0000";
name = "Feb 17 test";
order = 2;
})
Fyi, user1226119's answer (below) reminded me that I used the Organizer to extract the sqlite db from my device and inspect it with SQLite Manager to verify things. Sure enough there is still no new activationData field in the Blueprint table. The table looks the same as it always did.
I think I must have missed some necessary step for adding a new Attribute to an existing db Entity.
Your model has not change in your app. You must delete your old application and re-deploy your app on your device.
The solution was to update the pathForResource method call in the code that returns the NSManagedObjectModel. I had indeed created a new xcdatamodel version of the db before adding the attribute, but apparently you are supposed to refer to it using the following code, which retrieves the model your app will use.
- (NSManagedObjectModel *)managedObjectModel {
if (managedObjectModel != nil) {
return managedObjectModel;
}
NSString *path = [[NSBundle mainBundle] pathForResource:#"MyDB Version5" ofType:#"mom" inDirectory:#"ASSIST.momd"];
NSURL *momURL = [NSURL fileURLWithPath:path];
managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL];
return managedObjectModel;
}
I had to put the new database version's name ("MyDB Version5") as the pathForResource parameter. Previously it was "MyDB Version5".
I have app that stores tree structure in CoreData.
There is an ManagedObject, "Item", and it has attributes:
itemId (string)
List item
title (string)
parentId (string)
parent (relationship to Item)
parentTitle (string)
parentId points to another Item object.
How do I make property parentTitle to be filled automatically with title of parent Item ?
While Martin's suggestion is a good solution for derived values, my question on yours is, why would you want this? You are not manipulating the value from the parent at all, ever. Since you are just accessing it, access the parent directly via KVC such as:
Item *item = ...;
NSString *title = [item valueForKeyPath:#"parent.title"];
//Do something with title
The only time you would want to use the keyPathsForValues... functionality is if you are changing something based on that value. If you are just accessing it, use KVC directly.
This is a possibility to achieve the desired functionality:
// implement in Item.m
// manages KVO notifications
+ (NSSet *)keyPathsForValuesAffectingParentTitle
{
return [NSSet setWithObjects:#"parent.title", nil];
}
// getter for parentTitle
- (NSString*) parentTitle
{
return [self valueForKeyPath:#"parent.title"];
}
additionally declare the property for parentTitle as readonly in Item.h
There is no need to declare a Core Data attribute "parentTitle".
The only problem I see with this solution is the following:
Item A is parent of item B
A gets turned into fault
B is still active and some View is bound to B.parentTitle
The view gets a notification because of the dependency declared with keyPathsForValuesAffecting, still object A is already faulted (and on shutdown unable to be unfaulted again) does Core Data manage such faulting&observation problems automatically?