I'm currently having trouble querying data that I stored in an Inverse relationship. I have the following code
class Form: Object {
dynamic var id: String = NSUUID().uuidString
...
var answers = List<FormAnswer>()
override static func primaryKey() -> String? {
return "id"
}
...
}
and
class FormAnswer: Object {
dynamic var key = ""
dynamic var answer = ""
let form = LinkingObjects(fromType: Form.self, property: "answers")
override static func primaryKey() -> String? {
return "key"
}
}
When I create a FormAnswer object I do the following:
try! realm.write {
let answer = FormAnswer(value: ["key": key, "answer": answer, "form" : parentForm!]) // parentForm is of type "form"
realm.add(answer, update: true)
}
And when I try to query it, I get nothing!
let previousValue = realm.objects(FormAnswer.self).filter("key == %# AND ANY form.id == %#", key, parentForm!.id).first?.answer
I've checked the realm file with Realm Browser, and there's an entry for FormAnswer. But there are only 2 fields (key and answer) and there doesn't appear to be a link to my Form object.
Does anyone have any ideas on how I can fix this?
Thanks
LinkingObjects is a computed property and cannot be mutated directly. Instead you modify its values by changing the other side of the relationship.
Try:
try! realm.write {
parentForm.answers.add(FormAnswer(value: ["key": key, "answer": answer]))
}
This adds the new answer directly to the Form's answer list, and will result in the answer's form property containing parentForm.
Related
I think I'm introducing some logic error and I might be missing something here.
Please consider the following code:
// Model
class MyModel: NSObject {
let month: Int
let destiny: String
init(month: Int, destiny: String) {
self.month = month
self.destiny = destiny
}
}
var datasource: [MyModel] = []
var dict: [Int : [MyModel]] = [:]
func fillDatasource() {
for _ in 0...20 {
let month = Int.random(in: 1...12)
let destiny = "Any"
let model = MyModel(month: month, destiny: destiny)
datasource.append(model)
}
}
func fillDict() {
datasource.forEach {
let month = $0.month
dict[month]?.append($0)
}
print(dict) // always empty
}
fillDatasource()
fillDict()
Inside my fillDict function the array is always nil.
I think this is because the key doesn't exist , so the value cannot be appended to that specific key.
My question is: if the key doesn't exist, calling the append function would insert the key as well?
Am I missing something here?
Thanks.
Your assumption is incorrect and there is no reason to think that this would insert a new array.
It might seem intuitive for this case but it may be very wrong for some cases. How about something like this:
garages[myName]?.parkCar(myCar)
Should this construct a new garage for my car? I think not. But even if so; what if default constructor is unavailable and this is actually defined as a protocol:
protocol Garage {
func parkCar(_ car: Car)
}
var garages[String: Garage]
there is no way for Swift to fill in this object automatically.
Technically there would be a possible solution for this work that Swift would automatically construct an object for you in dictionary if this object had a default constructor and possibly the object type is a struct or a final class... But this would most likely only introduce more confusion than it would solve.
The most straight forward solution to your example is what #Sh_Khan wrote (but later deleted) which is:
if dict[month] == nil {
dict[month] = [$0]
}
else {
dict[month]?.append($0)
}
Probably some more feasible approach would be
dict[month] = (dict[month] ?? []) + [$0]
but as described in a comment there is already a method that does exactly that for you:
dict[month, default: []].append($0)
I hope we can agree that this is a more general approach and it fixes all cases. For instance
garages[myName, default: PublicGarage(parkingSpot: myName)].parkCar(myCar)
You can update your fillDict method to the following:
func fillDict() {
datasource.forEach {
let month = $0.month
if dict.keys.contains(month) {
dict[month]?.append($0)
} else {
dict[month] = [$0]
}
}
print(dict)
}
Explanation:
We need to check if the month key already exits in the dictionary, than append in it's array else we are assigning a new array against a month in the dictionary
Dic is empty because dic[month] is nil, the value has never been altered.
To group array by a property of the array elem, I'd use the following:
dic = Dictionary(grouping: datasource) { (model) -> Int in
return model.month
}
I'm using RealmSwift in my project.
When trying to update one of the parameters of an existing object, I get the following error:
Ambiguous reference to member 'create(_:value:update:)'
And here is the code I'm working on:
let newProduct = ShoppingBagObject(value: [product.id, product.name!, product.price!, product.oldPrice!, product.weight!, count])
try? realm?.write {
realm?.create(newProduct, value: ["count": 3], update: .modified)
}
I want to update the 'count' parameter only.
And here is the reference from realm.io official documentation:
try! realm.write {
realm.create(Book.self, value: ["id": 1, "price": 9000.0], update: .modified)
// the book's `title` property will remain unchanged.
}
EDIT:
Here is my model class:
class ShoppingBagObject: Object {
#objc dynamic var id = 0
#objc dynamic var name = ""
#objc dynamic var price = 0
#objc dynamic var oldPrice = 0
#objc dynamic var weight = 0
#objc dynamic var count = 1
override static func primaryKey() -> String? {
return "id"
}
}
What am I doing wrong ?
Can you try
try? realm?.write {
realm?.create(ShoppingBagObject.self, value: ["id":product.id, "count":3], update: .modified)
}
From the docs:
If a Book object with a primary key value of ‘1’ already exists in the
database, then that object will simply be updated. If it does not
exist, then a completely new Book object will be created and added to
the database.
You can also partially update objects with primary keys by passing
just a subset of the values you wish to update, along with the primary
key
Based on the following code I would like to be able to create a new ItemList from an existing one. In other words I have an ItemList called First List and I want to create a new ItemList, call it Second List and fill it with the Items from First List.
The way I have it right now is that it creates the Second List as expected, the Items from the First List show in Second List but what doesn't work is when I want to delete only the Items from First List, it deletes Items from both lists. I guess I'm not truly copying the items.
So the question is, how can I copy Items from First List to Second List?
Object Models:
class ItemList: Object {
dynamic var listName = ""
dynamic var createdAt = NSDate()
let items = List<Item>()
}
class Item:Object{
dynamic var productName:String = ""
dynamic var createdAt = NSDate()
}
Code to create Second List from First List
This Works fine, it creates Second List and adds the items from First List but I don't think I'm making copies just showing them in Second List.
let newList = ItemList()
newList.listName = "Second List"
if let selectedList = realm.objects(ItemList.self).filter("listName = %#", "First List").first{
let itemsFromFirstList = selectedList.items
newList.items.append(objectsIn:itemsFromFirstList)
}
try! realm.write {
realm.add(newList)
}
This code is supposed to delete only the items from First List
This actually deletes items from both First List and Second List
let listToDelete = realm.objects(ItemList.self).filter("listName = %#", "First List").first
try! realm.write {
for item in (listToDelete?.items)! {
realm.delete(realm.objects(Item.self).filter("productName = %#", item.productName).first!)
}
}
What you want to do is use:
for record in postsDB.objects(PostModel.self) {
if !combinedDB.objects(PostModel.self).filter("postId == \(record.parentId)").isEmpty {
combinedDB.create(PostModel.self, value: record, update: false)
}
}
The create method is inherited from Object. It tells the target to create a new object. Use true if you want it to look to see if there is already a record there, and update it if there is.
PostModel is the Object type, record is what you want copied.
Edit: I added the if statement to provide more context. You didn't show your class definitions, so I was guessing. This is a working example. I ask for a set of records from DatabaseA and copy it to DatabaseB (postsDB to combinedDB).
So if the type of the object you're trying to insert is a List, I'd recommend you define a subclass of Object, and have at least the list you need as a property.
class TagList: Object {
dynamic var tag = ""
var list = List<PostModel>()
override class func primaryKey() -> String? {
return "tag"
}
}
Full working example illustrating: creating new objects, copying all objects to a second list, deleting from second list after copying, adding to first list (which didn't get anything deleted from it.
import Foundation
import RealmSwift
class Letter: Object {
dynamic var letter = "a"
}
class Letters: Object {
var letterList = List<Letter>()
}
class ListExample {
let listRealmStore = try! Realm() // swiftlint:disable:this force_try
func testThis() {
print(Realm.Configuration.defaultConfiguration.fileURL!)
listRealmStore.beginWrite()
addSingleItems() // add 3 objects to the DB
let firstList = Letters()
let allObjects = listRealmStore.objects(Letter.self)
for item in allObjects {
firstList.letterList.append(item)
}
let secondList = Letters()
let itemsToCopy = firstList.letterList
for item in itemsToCopy {
let obj = listRealmStore.create(Letter.self)
obj.letter = item.letter
secondList.letterList.append(obj)
}
let third = Letter()
third.letter = "Z"
listRealmStore.add(third)
firstList.letterList.append(third)
secondList.letterList.removeLast()
do {
try listRealmStore.commitWrite()
} catch let error {
print("couldn't commit db writes: \(error.localizedDescription)")
}
print("list one:\n\(firstList)")
print("list two:\n\(secondList)")
}
func addSingleItems() {
for letter in ["a", "b", "c"] {
let objectToInsert = Letter()
objectToInsert.letter = letter
listRealmStore.add(objectToInsert)
}
}
}
Results in:
list one:
Letters {
letterList = List<Letter> (
[0] Letter {
letter = a;
},
[1] Letter {
letter = b;
},
[2] Letter {
letter = c;
},
[3] Letter {
letter = Z;
}
);
}
list two:
Letters {
letterList = List<Letter> (
[0] Letter {
letter = a;
},
[1] Letter {
letter = b;
}
);
}
Are you really trying to create copies of your items, or do you just want to be able to remove them from lists independently?
When you do:
newList.items.append(objectsIn: itemsFromFirstList)
you end up with the same objects being in both lists. List<T> just stores references to objects that live within the Realm. Appending an object to a List just references the existing object, it doesn't copy the object.
When you call Realm.delete(_:) you remove that object entirely from the Realm, not just from a single list that it is a member of. To remove an object from a List, you should instead use List.remove(objectAtIndex:).
One part the solution you are looking for could be like this, make copy objects in the list, or you can just use this idea to clone whole list it self:
Previously answered here
As of now, Dec 2020, there is not proper solution of this issue. We have many workarounds though.
Here is the one I have been using, and one with less limitations in my opinion.
Make your Realm Model Object classes conform to codable
class Dog: Object, Codable{
#objc dynamic var breed:String = "JustAnyDog"
}
Create this helper class
class RealmHelper {
//Used to expose generic
static func DetachedCopy<T:Codable>(of object:T) -> T?{
do{
let json = try JSONEncoder().encode(object)
return try JSONDecoder().decode(T.self, from: json)
}
catch let error{
print(error)
return nil
}
}
}
Call this method whenever you need detached / true deep copy of your Realm Object, like this:
//Suppose your Realm managed object: let dog:Dog = RealmDBService.shared.getFirstDog()
guard let detachedDog = RealmHelper.DetachedCopy(of: dog) else{
print("Could not detach Note")
return
}
//Change/mutate object properties as you want
detachedDog.breed = "rottweiler"
As you can see we are piggy backing on Swift's JSONEncoder and JSONDecoder, using power of Codable, making true deep copy no matter how many nested objects are there under our realm object. Just make sure all your Realm Model Classes conform to Codable.
Though its NOT an ideal solution, but its one of the most effective workaround.
Does anyone know how you can use Realm to store an array of strings? I'm trying to map the following response into Realm correctly:
"zoneInfo": {
"tariffInfoLines": [
"In this city you pay per minute."
]
}
We have a zoneInfo object that contains a tariffInfoLines array. This tariffInfoLines array contains strings. In Realm there are two different variable types for storing data. The first is RLMObject which allows your standard NSString, int, long etc.
The second type is RLMArray, which is used for arrays (as NSArray is not supported). You have to give the array a type, which must be a class that subclasses RLMObject. We have so far got around this by using a ABCRealmString object, as shown below:
#property RLMArray<ABCRealmString> *tariffInfoLines;
ABCRealmString contains an NSString property (it is basically a wrapper):
#property NSString *value;
However what this means is that when Realm tries to map the response to persist the data, it is looking for a value for the key "value" (the name of the property). It appears that it expects a response similar to the following:
"zoneInfo": {
"tariffInfoLines": [
{
"value": "In this city you pay per minute."
},
]
}
In the project, we have it working for the following structure:
"userOptions": [
{
"wantsEmailNotifications": true,
"wantsPushNotifications": false
},
]
This has an array, with objects inside that have clear key value pairs that Realm can map to. The zoneInfo structure appears to be the only place that we have an array with sets of values inside without them being inside an object or having any keys.
If anyone could shed some light on this, regarding if this is possible using Realm, or whether an API change is required to match a structure that Realm can map.
Cross posting from the github issue response: Although this example demonstrates how to store flat arrays of strings on a Realm model, you can extend this pattern to store anything from arrays of integers to native Swift enum's. Basically anything that you can map to a representable type in Realm.
class RealmString: Object {
dynamic var stringValue = ""
}
class Person: Object {
var nicknames: [String] {
get {
return _backingNickNames.map { $0.stringValue }
}
set {
_backingNickNames.removeAll()
_backingNickNames.appendContentsOf(newValue.map({ RealmString(value: [$0]) }))
}
}
let _backingNickNames = List<RealmString>()
override static func ignoredProperties() -> [String] {
return ["nicknames"]
}
}
// Usage...
let realm = try! Realm()
try! realm.write {
let person = Person()
person.nicknames = ["John", "Johnny"]
realm.add(person)
}
for person in realm.objects(Person) {
print("Person's nicknames: \(person.nicknames)")
}
// Prints:
// Person's nicknames: ["John", "Johnny"]
UPDATE (most of the previous answers are no longer correct):
You can now store primitive types or their nullable counterparts (more specifically: booleans, integer and floating-point number types, strings, dates, and data) directly within RLMArrays or Lists. If you want to define a list of such primitive values you no longer need to define cumbersome single-field wrapper objects. Instead, you can just store the primitive values themselves.
Lists of primitive values work much the same way as lists containing objects, as the example below demonstrates for Swift:
class Student : Object {
#objc dynamic var name: String = ""
let testScores = List<Int>()
}
// Retrieve a student.
let realm = try! Realm()
let bob = realm.objects(Student.self).filter("name = 'Bob'").first!
// Give him a few test scores, and then print his average score.
try! realm.write {
bob.testScores.removeAll()
bob.testScores.append(94)
bob.testScores.append(89)
bob.testScores.append(96)
}
print("\(bob.testScores.average()!)") // 93.0
All other languages supported by Realm also supports lists of primitive types.
For the Swift 3.0 here is the change (in my case the Xcode 8 compiler didn't offer auto fix when i switched to swift 3.0 so I had some pain to resolve it).
_backingNickNames.append(objectsIn: newValue.map { RealmString(value: [$0]) })
The RealmString approach is good, but you end up with a new RealmString every time you update the values, leaving a ton of unused objects laying around if you don't clean them up.
I would suggest using something like:
fileprivate let separator = "\u{FFFF}"
class Person: Object {
fileprivate dynamic var _nicknames: String?
var nicknames: [String] {
get { return _nicknames?.components(separatedBy: separator) ?? [] }
set { _nicknames = newValue.isEmpty ? nil : newValue.joined(separator: separator) }
}
override static func ignoredProperties() -> [String] {
return ["nicknames"]
}
}
extension String {
func toStringObject() -> StringObject {
return StringObject(initValue: self)
}
}
extension Sequence where Iterator.Element == String {
func toStringObjects() -> List<StringObject> {
let list = List<StringObject>()
for s in self {
list.append(s.toStringObject())
}
return list
}
}
extension Int {
func toIntObject() -> IntObject {
return IntObject(initValue: self)
}
}
extension Sequence where Iterator.Element == Int {
func toIntObjects() -> List<IntObject> {
let list = List<IntObject>()
for s in self {
list.append(s.toIntObject())
}
return list
}
}
For now I am using this fetching with Predicate to know if the same primary key value is already available:
Category class:
class Category: Object
{
dynamic var name = ""
override static func primaryKey() -> String? {
return "name"
}
}
Validating if Category Object with primary key (name) value already exists.
let predicate = NSPredicate(format: "name == %#", newCategoryName)
let realm = try Realm()
let categories = realm.objects(Category).filter(predicate).sorted("name")
if categories.count > 0
{
//Duplicate Object with newCategoryName found
}
Is there any simpler way?
Here's how you use it to check if there's already an object with that primary key:
let category = Realm().objectForPrimaryKey(Category.self, key: newCategoryName)
if (category != nil) {
//Duplicate Object with newCategoryName found
}
You can use Realm.add(_:update:) or Realm.create(_:update:) with update == true to update an existing object with the same primary key value. Alternatively, you can use Realm.objectForPrimaryKey(_:key:) to fetch an existing object from the primary key.