I have a Core Data entity with two attributes (title and time), both String. How can I access the time attribute by knowing the title and how can I modify the time property later?
I can access the title with a predicate but I don't know how to get and modify the title
func getTime(title: String, entityName: String) {
let request: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: entityName)
request.predicate = NSPredicate(format: "title == %#", title)
}
Your function is not returning anything.
You still need to do a request, not only declaring it.
do {
let fetchedTimes = try context.executeFetchRequest(request) as! [Time]
return fetchedTimes
} catch {
fatalError("Failed to fetch times: \(error)")
}
Change function:
func getTime(title: String, entityName: String) -> [time] {
Related
I have to following class type
class Recipe {
private let id: CKRecord.ID
let name: String
let coverPhoto: CKAsset?
init?(record: CKRecord, database: CKDatabase) {
guard
let name = record["name"] as? String
else { return nil }
id = record.recordID
self.name = name
coverPhoto = record["coverPhoto"] as? CKAsset
}
and in my viewcontroller, I want to display list of names that I fetched from cloudkit. So, i am trying to find a way to convert CKRecord to my class type Recipe.
I tried this but failed
let query = CKQuery(recordType: "GroceryItem", predicate: NSPredicate(value:true))
database.perform(query, inZoneWith: nil) { [weak self] records, error in
guard let records = records,error == nil else {
return
}
DispatchQueue.main.async {
self?.items = records.compactMap({ $0.value as? Recipe }) // gives error ambigous value
self?.tableView.reloadData()
}
}
Records is the fetched variable from cloudkit as CKRecord
items is array of Recipe, [Recipe]
I want to transfer the data from records to items.
You cannot cast the type. You have to call init.
First remove the database parameter from the init method, it’s obviously not needed
init?(record: CKRecord) { …
Then replace
self?.items = records.compactMap({ $0.value as? Recipe })
with
self?.items = records.compactMap(Recipe.init)
I'm trying to fetch all my items from Core Data that doesn't have "X" in its allergens attribute.
func doesNotContain(attribute: String = "allergens", text: String) {
let request: NSFetchRequest<Dinner> = Dinner.fetchRequest()
let predicate = NSPredicate(format:"NOT \(attribute) CONTAINS %#", text)
request.predicate = predicate
do { items = try context.fetch(request) }
catch let error { print("Error: \(error)") }
}
For some reason this crashes with "EXC_BAD_ACCESS"
But it works perfectly fine when I'm trying to fetch with a predicate using:
func containsSearchWithNSPredicate(attribute: String, text: String) {
let request: NSFetchRequest<Dinner> = Dinner.fetchRequest()
let predicate = NSPredicate(format: "\(attribute) CONTAINS[cd] %#", text)
request.predicate = predicate
do { items = try context.fetch(request) }
catch let error { print("Error: \(error)") }
}
The attribute here is set to "name" when the function is called, and it's set to "allergens" in the first example
I've made sure that the attribute "allergens" is not nil, and I've also tried using %d instead of %#. The allergens attribute is an array, and that's why I'm using NOT CONTAINS
Turns out that NSPredicate doesn't work with attributes marked as "Transformable" with a custom class of [String].
I made it work by instead of having an array, I made it to a String, separating each individual allergen with ";" to make it possible to divide into substrings later.
allergen example:
dinner.allergens = "Gluten;Dairy"
The NSPredicate:
let predicate = NSPredicate(format:"NOT (%K CONTAINS[cd] %#)",attribute, text)
The fetch request will now get all entities that does not have an allergen attribute containing text
In Swift 2 the following code was working:
let request = NSFetchRequest(entityName: String)
but in Swift 3 it gives error:
Generic parameter "ResultType" could not be inferred
because NSFetchRequest is now a generic type. In their documents they wrote this:
let request: NSFetchRequest<Animal> = Animal.fetchRequest
so if my result class is for example Level how should I request correctly?
Because this not working:
let request: NSFetchRequest<Level> = Level.fetchRequest
let request: NSFetchRequest<NSFetchRequestResult> = Level.fetchRequest()
or
let request: NSFetchRequest<Level> = Level.fetchRequest()
depending which version you want.
You have to specify the generic type because otherwise the method call is ambiguous.
The first version is defined for NSManagedObject, the second version is generated automatically for every object using an extension, e.g:
extension Level {
#nonobjc class func fetchRequest() -> NSFetchRequest<Level> {
return NSFetchRequest<Level>(entityName: "Level");
}
#NSManaged var timeStamp: NSDate?
}
The whole point is to remove the usage of String constants.
I think i got it working by doing this:
let request:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Level")
at least it saves and loads data from DataBase.
But it feels like it is not a proper solution, but it works for now.
The simplest structure I found that works in 3.0 is as follows:
let request = NSFetchRequest<Country>(entityName: "Country")
where the data entity Type is Country.
When trying to create a Core Data BatchDeleteRequest, however, I found that this definition does not work and it seems that you'll need to go with the form:
let request: NSFetchRequest<NSFetchRequestResult> = Country.fetchRequest()
even though the ManagedObject and FetchRequestResult formats are supposed to be equivalent.
Here are some generic CoreData methods that might answer your question:
import Foundation
import Cocoa
func addRecord<T: NSManagedObject>(_ type : T.Type) -> T
{
let entityName = T.description()
let context = app.managedObjectContext
let entity = NSEntityDescription.entity(forEntityName: entityName, in: context)
let record = T(entity: entity!, insertInto: context)
return record
}
func recordsInTable<T: NSManagedObject>(_ type : T.Type) -> Int
{
let recs = allRecords(T.self)
return recs.count
}
func allRecords<T: NSManagedObject>(_ type : T.Type, sort: NSSortDescriptor? = nil) -> [T]
{
let context = app.managedObjectContext
let request = T.fetchRequest()
do
{
let results = try context.fetch(request)
return results as! [T]
}
catch
{
print("Error with request: \(error)")
return []
}
}
func query<T: NSManagedObject>(_ type : T.Type, search: NSPredicate?, sort: NSSortDescriptor? = nil, multiSort: [NSSortDescriptor]? = nil) -> [T]
{
let context = app.managedObjectContext
let request = T.fetchRequest()
if let predicate = search
{
request.predicate = predicate
}
if let sortDescriptors = multiSort
{
request.sortDescriptors = sortDescriptors
}
else if let sortDescriptor = sort
{
request.sortDescriptors = [sortDescriptor]
}
do
{
let results = try context.fetch(request)
return results as! [T]
}
catch
{
print("Error with request: \(error)")
return []
}
}
func deleteRecord(_ object: NSManagedObject)
{
let context = app.managedObjectContext
context.delete(object)
}
func deleteRecords<T: NSManagedObject>(_ type : T.Type, search: NSPredicate? = nil)
{
let context = app.managedObjectContext
let results = query(T.self, search: search)
for record in results
{
context.delete(record)
}
}
func saveDatabase()
{
let context = app.managedObjectContext
do
{
try context.save()
}
catch
{
print("Error saving database: \(error)")
}
}
Assuming that there is a NSManagedObject setup for Contact like this:
class Contact: NSManagedObject
{
#NSManaged var contactNo: Int
#NSManaged var contactName: String
}
These methods can be used in the following way:
let name = "John Appleseed"
let newContact = addRecord(Contact.self)
newContact.contactNo = 1
newContact.contactName = name
let contacts = query(Contact.self, search: NSPredicate(format: "contactName == %#", name))
for contact in contacts
{
print ("Contact name = \(contact.contactName), no = \(contact.contactNo)")
}
deleteRecords(Contact.self, search: NSPredicate(format: "contactName == %#", name))
recs = recordsInTable(Contact.self)
print ("Contacts table has \(recs) records")
saveDatabase()
This is the simplest way to migrate to Swift 3.0, just add <Country>
(tested and worked)
let request = NSFetchRequest<Country>(entityName: "Country")
Swift 3.0 This should work.
let request: NSFetchRequest<NSFetchRequestResult> = NSManagedObject.fetchRequest()
request.entity = entityDescription(context)
request.predicate = predicate
I also had "ResultType" could not be inferred errors. They cleared once I rebuilt the data model setting each entity's Codegen to "Class Definition". I did a brief writeup with step by step instructions here:
Looking for a clear tutorial on the revised NSPersistentContainer in Xcode 8 with Swift 3
By "rebuilt" I mean that I created a new model file with new entries and attributes. A little tedious, but it worked!
What worked best for me so far was:
let request = Level.fetchRequest() as! NSFetchRequest<Level>
I had the same issue and I solved it with the following steps:
Select your xcdatamodeld file and go to the Data Model Inspector
Select your first Entity and go to Section class
Make sure that Codegen "Class Definition" is selected.
Remove all your generated Entity files. You don't need them anymore.
After doing that I had to remove/rewrite all occurences of fetchRequest as XCode seem to somehow mix up with the codegenerated version.
HTH
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
func loadItemsCategory() {
let request: NSFetchRequest<Category> = Category.fetchRequest()
do {
categoryArray = try context.fetch(request)
} catch {
print(error)
}
tableView.reloadData()
}
I have a Core Data entity (type) called NoteEntity. It has a managed variable called noteDocument, which is of the custom type NoteDocument (my subclass of NSDocument). I changed its auto-generated NoteEntity+Core Data Properties class so it reads
import Foundation
import CoreData
extension NoteEntity {
#NSManaged var noteDocument: NoteDocument? // changed
#NSManaged var belongsTo: NSSet?
}
so that noteDocument is of type NoteDocument instead of NSObject. The NoteDocument class does implement NSCoding, as follows:
required convenience init(coder theDecoder: NSCoder)
{
let retrievedURL = theDecoder.decodeObjectForKey("URLKey") as! NSURL
self.init(receivedURL: retrievedURL)
}
func encodeWithCoder(theCoder: NSCoder)
{
theCoder.encodeObject(fileURL, forKey: "URLKey")
}
What I want to be able to do is find the noteEntity entities in the managed context with a given noteDocument value. So I run this code (passing it a parameter theNote that corresponds to a noteDocument that I know exists in the managed context):
var request = NSFetchRequest(entityName: "NoteEntity")
let notePredicate = NSPredicate(format: "noteDocument == %#", theNote)
request.predicate = notePredicate
print("Text in the NoteEntity with the NoteDocument for "+theNote.filename+":")
do
{
let notesGathered = try context.executeFetchRequest(request) as? [NoteEntity]
for n in notesGathered!
{
print (n.noteDocument!.filename)
print (n.noteDocument!.noteText)
}
}
catch let error as NSError
{
print("Could not run fetch request. \(error), \(error.userInfo)")
}
but it returns no entries. If I comment out the predicate, I get all the NoteEntity values in the database, but with the predicate in there I get nothing. Clearly something is wrong with the search I'm trying to do in the predicate. I think it's because the value is a Transformable, but I'm not sure where to go from there. I know you can't run fetch requests on the members of Transformable arrays, but is it not possible to run fetch requests on single Transformable attributes? If it isn't, what alternatives exist?
EDIT: The NoteDocument class includes a lot more than the NSCoding. As I said, it's an NSDocument subclass. The NSCoding uses a URL as its key because that's the "primary key" for the NoteDocument class - it's what initializes the class. Here is the rest of the class, not including the NSCoding above:
import Cocoa
class NoteDocument: NSDocument, NSCoding
{
var filename: String
var noteText: String
var attributes: NSDictionary?
var dateCreated: NSDate?
var dateString: String?
init (receivedURL: NSURL)
{
self.filename = ""
self.noteText = ""
super.init()
self.fileType = "net.daringfireball.markdown"
self.fileURL = receivedURL
// Try to get attributes, most importantly date-created.
let fileManager = NSFileManager.defaultManager()
do
{
attributes = try fileManager.attributesOfItemAtPath(fileURL!.path!)
}
catch let error as NSError
{
print("The error was: "+String(error))
}
if let dateCreated = attributes?.fileCreationDate()
{
// print("dateCreated is "+String(dateCreated!))
// Format the date-created to an appropriate string.
dateString = String(dateCreated)
}
else
{
print("Did not find the attributes for "+filename)
}
if let name = self.fileURL?.lastPathComponent
{
filename = name
}
else
{
filename = "Unnamed File"
}
noteText = ""
do
{
noteText = try NSString(contentsOfURL: self.fileURL!, encoding: NSUTF8StringEncoding) as String
}
catch let error as NSError
{
print("Error trying to get note file:"+String(error))
}
}
// MARK: - Document functions
override class func autosavesInPlace() -> Bool
{
// print ("autosavesInPlace ran.")
return true
}
override func dataOfType(typeName: String) throws -> NSData
{
var outError: NSError! = NSError(domain: "Migrator", code: 0, userInfo: nil)
// Post: Document is saved to a file specified by the user.
outError = NSError(domain: NSOSStatusErrorDomain, code: unimpErr, userInfo: nil)
if let value = self.noteText.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false) {
// Convert noteText to an NSData object and return that.
return value
}
print("dataOfType ran.")
throw outError
}
override func readFromData(data: NSData, ofType typeName: String) throws
{
// Currently unused; came free with NSDocument.
throw NSError(domain: NSOSStatusErrorDomain, code: unimpErr, userInfo: nil)
}
}
In the code you show that the only thing you're coding is a URL. In this case it makes much more sense and provides more utility to use a plain string in the entity to store the URL and to add a transient attribute (or create a wrapper class to combine the entity and document) for the document. In this way you can use the URL in the predicate and it's easy to build the predicate from a document. Storing the document as a transformable isn't helping you in any way it seems.
In Swift 2 the following code was working:
let request = NSFetchRequest(entityName: String)
but in Swift 3 it gives error:
Generic parameter "ResultType" could not be inferred
because NSFetchRequest is now a generic type. In their documents they wrote this:
let request: NSFetchRequest<Animal> = Animal.fetchRequest
so if my result class is for example Level how should I request correctly?
Because this not working:
let request: NSFetchRequest<Level> = Level.fetchRequest
let request: NSFetchRequest<NSFetchRequestResult> = Level.fetchRequest()
or
let request: NSFetchRequest<Level> = Level.fetchRequest()
depending which version you want.
You have to specify the generic type because otherwise the method call is ambiguous.
The first version is defined for NSManagedObject, the second version is generated automatically for every object using an extension, e.g:
extension Level {
#nonobjc class func fetchRequest() -> NSFetchRequest<Level> {
return NSFetchRequest<Level>(entityName: "Level");
}
#NSManaged var timeStamp: NSDate?
}
The whole point is to remove the usage of String constants.
I think i got it working by doing this:
let request:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Level")
at least it saves and loads data from DataBase.
But it feels like it is not a proper solution, but it works for now.
The simplest structure I found that works in 3.0 is as follows:
let request = NSFetchRequest<Country>(entityName: "Country")
where the data entity Type is Country.
When trying to create a Core Data BatchDeleteRequest, however, I found that this definition does not work and it seems that you'll need to go with the form:
let request: NSFetchRequest<NSFetchRequestResult> = Country.fetchRequest()
even though the ManagedObject and FetchRequestResult formats are supposed to be equivalent.
Here are some generic CoreData methods that might answer your question:
import Foundation
import Cocoa
func addRecord<T: NSManagedObject>(_ type : T.Type) -> T
{
let entityName = T.description()
let context = app.managedObjectContext
let entity = NSEntityDescription.entity(forEntityName: entityName, in: context)
let record = T(entity: entity!, insertInto: context)
return record
}
func recordsInTable<T: NSManagedObject>(_ type : T.Type) -> Int
{
let recs = allRecords(T.self)
return recs.count
}
func allRecords<T: NSManagedObject>(_ type : T.Type, sort: NSSortDescriptor? = nil) -> [T]
{
let context = app.managedObjectContext
let request = T.fetchRequest()
do
{
let results = try context.fetch(request)
return results as! [T]
}
catch
{
print("Error with request: \(error)")
return []
}
}
func query<T: NSManagedObject>(_ type : T.Type, search: NSPredicate?, sort: NSSortDescriptor? = nil, multiSort: [NSSortDescriptor]? = nil) -> [T]
{
let context = app.managedObjectContext
let request = T.fetchRequest()
if let predicate = search
{
request.predicate = predicate
}
if let sortDescriptors = multiSort
{
request.sortDescriptors = sortDescriptors
}
else if let sortDescriptor = sort
{
request.sortDescriptors = [sortDescriptor]
}
do
{
let results = try context.fetch(request)
return results as! [T]
}
catch
{
print("Error with request: \(error)")
return []
}
}
func deleteRecord(_ object: NSManagedObject)
{
let context = app.managedObjectContext
context.delete(object)
}
func deleteRecords<T: NSManagedObject>(_ type : T.Type, search: NSPredicate? = nil)
{
let context = app.managedObjectContext
let results = query(T.self, search: search)
for record in results
{
context.delete(record)
}
}
func saveDatabase()
{
let context = app.managedObjectContext
do
{
try context.save()
}
catch
{
print("Error saving database: \(error)")
}
}
Assuming that there is a NSManagedObject setup for Contact like this:
class Contact: NSManagedObject
{
#NSManaged var contactNo: Int
#NSManaged var contactName: String
}
These methods can be used in the following way:
let name = "John Appleseed"
let newContact = addRecord(Contact.self)
newContact.contactNo = 1
newContact.contactName = name
let contacts = query(Contact.self, search: NSPredicate(format: "contactName == %#", name))
for contact in contacts
{
print ("Contact name = \(contact.contactName), no = \(contact.contactNo)")
}
deleteRecords(Contact.self, search: NSPredicate(format: "contactName == %#", name))
recs = recordsInTable(Contact.self)
print ("Contacts table has \(recs) records")
saveDatabase()
This is the simplest way to migrate to Swift 3.0, just add <Country>
(tested and worked)
let request = NSFetchRequest<Country>(entityName: "Country")
Swift 3.0 This should work.
let request: NSFetchRequest<NSFetchRequestResult> = NSManagedObject.fetchRequest()
request.entity = entityDescription(context)
request.predicate = predicate
I also had "ResultType" could not be inferred errors. They cleared once I rebuilt the data model setting each entity's Codegen to "Class Definition". I did a brief writeup with step by step instructions here:
Looking for a clear tutorial on the revised NSPersistentContainer in Xcode 8 with Swift 3
By "rebuilt" I mean that I created a new model file with new entries and attributes. A little tedious, but it worked!
What worked best for me so far was:
let request = Level.fetchRequest() as! NSFetchRequest<Level>
I had the same issue and I solved it with the following steps:
Select your xcdatamodeld file and go to the Data Model Inspector
Select your first Entity and go to Section class
Make sure that Codegen "Class Definition" is selected.
Remove all your generated Entity files. You don't need them anymore.
After doing that I had to remove/rewrite all occurences of fetchRequest as XCode seem to somehow mix up with the codegenerated version.
HTH
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
func loadItemsCategory() {
let request: NSFetchRequest<Category> = Category.fetchRequest()
do {
categoryArray = try context.fetch(request)
} catch {
print(error)
}
tableView.reloadData()
}