So I'm trying to update a List property of an Object class in Realm. The property of the Object updates, but for some reason when it gets to the Realm, the update never occurs. In other words, I've confirmed that the changes have been made to the actual object just after I made the changes(the List updates in the object), but after I add to the realm, and then get the object back from the realm, it's as if nothing ever changed. Here is the code:
do{
try! realm.write{
let course = realm.objects(Course.self).filter("id =='\(courseID!)'").first
course!.days = List<String>()
for day in daysSelected{
course?.days.append(day)
}
realm.add(course!, update: .modified)
}
}catch{
print(error)
}
Also, you should know that when I update other properties like Strings, the changes go through just fine. Am I doing something wrong with lists? In my object class, the list is declared as:
var days: List<String> = List<String>()
According to the documentation:
Properties of List type defined on Object subclasses must be declared
as let and cannot be dynamic.
Rather than defining your list as:
var days: List<String> = List<String>()
Define it as:
let days = List<String>()
Related
I need to query MongoDB Realm from synced iOS and Android app. In Swift I can write something like this:
let dictionary = realm?.objects(myReamlObject.self)
let results = dictionary?.where {
$0.senses.glosses.term == "the term I want"
}
or using predicate:
let results = dictionary?.filter("ANY senses.glosses.term == %#", "the term I want")
Both work well, but I don't want to check ALL senses.glosses.term.
Every entry has (or could have) many senses and many glosses.
I would like to check term of first senses in first glosses only.
Something I would write like this:
let results = dictionary?.where {
$0.senses[0].glosses[0].term == "the term I want"
}
But it gives error:
Referencing subscript 'subscript(_:)' on 'Query' requires that
'List<myRealmObject_senses>' conform to 'RealmKeyedCollection'
Any suggestion on how to query only first index of an array in MongoDB Realm? Thank you
Let me re-state the question
How to query a Realm objects' List property - but only query on the first
element in the List.
The answer is going to depend on the amount of results being worked with.
Here's how to do it in a way that's O.K. for small datasets but NOT RECOMMENDED
Your models were not included in the question so let me use a simplified model of a PersonClass that as a List of DogClass objects
class PersonClass: Object {
#Persisted var name = ""
#Persisted var dogList = List<DogClass>()
}
class DogClass: Object {
#Persisted var name = ""
}
The idea here is to use Swift high-level functions to only test the first item in each persons doglist for a match (this can be applied to other languages as well)
//get all the people
let peopleResults = realm.objects(PersonClass.self)
//use the high-level Swift function compactMap to return all of
// the people whose first dog is named "Spot"
let persons = peopleResults.compactMap { person -> PersonClass? in
if person.dogList.first?.name == "Spot" {
return person
}
return nil
}
The downside is that this code overrides a fundamental advantage of Realm - that Realm objects are lazily loaded if Realm functions are used e.g. as soon as a high-level Swift function is used, ALL of the objects are loaded into memory, potentially overwhelming the device.
A better option is to simply add a managed property to the PersonClass that also points to the 0'th element in the list.
class PersonClass: Object {
#Persisted var name = ""
#Persisted var dogList = List<DogClass>()
#Persisted var mainDog: DogClass?
func addMainDog(withDog: DogClass) {
self.dogList.append(withDog)
self.mainDog = withDog
}
}
as you can see, there's also a function to add that first dog to the list and also populates the mainDog property which points to the same object. It's one property so the overall impact is very low but the advantages for simple queries are very high.
From there the query becomes trivial
let peopleResults = realm.objects(PersonClass.self).where { $0.mainDog.name == "Spot" }
Expanding on this, you could save the 0th element of each List object in the Parent object or even have a property in each child object that points to the first element in it's respective list.
I would like to perform this filter method using NSPredicate, but I'm having trouble converting the syntax.
objectsCollection.filter { $0.stringIds.contains(id) }
Sample class
class Object {
let stringIds: [String]
}
let objectsCollection: [Object]
let id = "The id we want to look for"
objectsCollection.filter { $0.stringIds.contains(id) }
My attempt with NSPredicate
This is how I thought it would work, but seems like it doesn't.
let filter = NSPredicate(format: "%# IN stringIds", id)
objectsCollection.filter(filter)
Error
reason: 'Expected object of type (null) for property 'stringIds' on object of type 'Object', but received: 6011ea4dda6853a3af97376e'
There are a few issues that need to be addressed.
This
let stringIds: [String]
is not a realm object and will not be persisted in Realm.
That needs to be a List property and the object type of the list is another Realm object. Realm Lists do not support primitives (very well). Also, don't name your objects the same name as another object.
class MyClass: Object {
let myStringIdList = List<MyStringIdClass>
}
and
class MyStringIdClass: Object {
#objc dynamic var myId = ""
}
to then get all of the MyClass objects that had a certain stringId in their list
let results = realm.objects(MyClass.self).filter("ANY myStringIdList.myId == %#", idToFind)
The string inside .filter can also be an NSPredicate if needed.
You can also use LinkingObjects to navigate back to the MyClass objects as well.
One other thing, when you cast realm objects to an array, they loose their connection to realm and are no longer live updating objects.
Also, Realm objects are lazily loaded meaning that thousands of objects have very little memory impact. Casting them to an array however, loads ALL of that data and can overwhelm the device with a large data set.
I am currently trying out Realm on a test project and I have been struggling with removing a specific object from a List. LensDBObject and ListDBObject. LensDBObject contains a list of lenses and ListDBObject are lists of existing lenses. A lens can be in multiple lists and I'd like to remove a specific lens from a specific list but not remove if from the other lists.
Below are my two classes:
#objcMembers class LensDBObject: Object {
dynamic var id = UUID().uuidString
dynamic var manufacturer = ""
dynamic var series = ""
dynamic var serial = ""
dynamic var isSelected = false
override static func primaryKey() -> String? {
return "id"
}
let objects = LinkingObjects(fromType: ListDBObject.self, property: "lensList")
}
#objcMembers class ListDBObject: Object {
dynamic var listName = ""
let lensList = List<LensDBObject>()
}
Below is my code to find a specific lens in the list I want. The values returned are what I expect.
let listToSearch = realm.objects(ListDBObject.self).filter("listName == %#", "List 542")
print(listToSearch)
let filteredResults = listToSearch[0].lensList.filter("manufacturer == %# AND series == %# AND serial == %#", "Panavision" , "Primo Prime", "407")
print(filteredResults)
However, when I try to delete filteredResults, it deletes it from the lensDBOject altogether. I just want to be able to delete this specific lens from this specific list.
try! realm.write {
realm.delete(filteredResults)
}
I tried using for loops to get the index of the lens in the list and then delete it directly from that. But it still deletes the lens everywhere.
Am I missing something? Should I be using a one-to-many relationship as opposed to a LinkingObject?
Thanks for you help!
Try something like this. You only want to remove the lens from the list, not delete it from the Realm.
try! realm.write {
filteredResults.forEach { lens in
if let index = listToSearch[0].lensList.index(of: lens) {
listToSearch[0].lensList.remove(at: index)
}
}
}
Note that this will remove from that one specific list all lenses that match your filter.
Edit: Updated to reflect Realm's custom List class.
The if let is required, because index(of:) could potentially return nil if the object is not found in the list. Additionally, we must do it one item at a time rather than getting all the indexes first, since removing an item would cause the index array to be wrong.
I'm trying to set data in a Realm database in swift via Object schema properties. Add new objects has been straightforward (and also relate and object to another), but I can't fin the way to append objects to a List property.
Let's see the snippet of code I use to create objects and add to Realm database:
func save(elements: [String : Any], realmClassName: String, realm: Realm, listObject: Object) {
// Ge properties for Realm Object subclass with name realmClassName
let properties = realm.schema[realmClassName]
// Iterate through elements array
for element in elements {
// Instantiate Realm Object through its name (realmClassName)
let thisClass: AnyClass = NSClassFromString("\(namespace).\(name)")!
let realmClass = thisClass as! Object.Type
let object = realmClass.init()
// Iterate though Object Schema properties
for property in properties?.properties as [Property]! {
object[property.name] = element[property.name]
}
// Add Object to Realm database
realm.add(object)
// Here is where I want to append object to Object List
}
}
Question is, how to do something similar to:
listObject.append(object)
Some attempt trow error like:
Could not cast value of type 'RealmSwift.List<AppName.Cars>' (0x1117446d8) to 'RealmSwift.List<RealmSwift.Object>'
Thanks.
Before i get too far into my question. My goal, which may influence your answers, is to remove Object data if it is no longer in the cloud.
So if I have an array ["one", "two", "three"]
Then in my server I remove "two"
I want my realm to update the change.
I figure the best way to do this is to delete all data in the specific Object, then call my REST API to download the new data. If there is a better way, please let me know.
Okay so here is my problem.
I have an Object Notifications()
every time my REST API is called, before it downloads anything I am running this:
let realm = Realm()
let notifications = Notifications()
realm.beginWrite()
realm.delete(notifications)
realm.commitWrite()
I get this error after running: Can only delete an object from the Realm it belongs to.
so i tried something like this:
for notification in notifications {
realm.delete(notification)
}
realm.commitWrite()
The error I get within xcode is this: "Type Notifications does not conform to protocol 'SequenceType'
Not really sure where to go from here.
Just trying to figure out realm. Completely new to it
Note: realm.deleteAll() works, but I don't want all of my realm deleted, just certain Objects
You're looking for this:
let realm = Realm()
let deletedValue = "two"
realm.write {
let deletedNotifications = realm.objects(Notifications).filter("value == %#", deletedValue)
realm.delete(deletedNotifications)
}
or perhaps this:
let realm = Realm()
let serverValues = ["one", "three"]
realm.write {
realm.delete(realm.objects(Notifications)) // deletes all 'Notifications' objects from the realm
for value in serverValues {
let notification = Notifications()
notification.value = value
realm.add(notification)
}
}
Although ideally, you'd be setting a primary key on Notifications so that you can simply update those existing objects rather than taking the extreme approach of nuking all your local objects simply to recreate them all (or almost).