I have a strange problem:
I have a NSManagedObject called ItemTemplate. It has many child managed objects, e.g. CustomItemTemplate or SpecialItemTemplate.
Now I have a list viewController that is supposed to show these child managed objects. For example only "CustomItemTemplaze" or only "SpecialItemTemplate". I wrote this generic method to fetch all ItemTemplates and filter out the desired child-objects (I haven't found a better way yet).
private func loadTemplates<T: ItemTemplate>(ofType type: T.Type) -> [ModelObject] {
// ModelObject is just a model for my managed objects
var templates = [ModelObject]()
do {
let request: NSFetchRequest<ItemTemplate> = ItemTemplate.fetchRequest()
let result = try mainViewContext.fetch(request)
for item in result {
if item is T { // this is somehow always true
templates.append(item.modelObject) // add the converted item to the array
}
}
} catch let error as NSError {
print("Error: ", error.debugDescription)
}
return templates
}
I call it like this:
enum Category {
case custom
case special
public var templateClass: ItemTemplate.Type {
switch self {
case .custom:
return CustomItemTemplate.self
case .special:
return SpecialItemTemplate.self
}
}
}
loadTemplates(ofType: currentCategory.templateClass)
However, it's not filtering. if item is T seems to be true for every item. It thus returns every ItemTemplate, instead of only certain child objects.
Why is that? I can't explain it.
Thanks for any help!
Related
This is my first question to the StackOverflow community so excuse me if I'm doing something wrong.
1. What I'm trying to achieve
Basically, I want to make a custom reactive wrapper around Eureka's SelectableSection class in order to observe the value of the selected row when it is changed. I'm thinking to get this data from the onSelectSelectableRow closure which is called every time a row is selected.
2. What I've tried to do for that
Actually, I've got this working but it's not a generic use of the custom wrapper, here is the example that works but only when I specify the row and its value type, for example ListCheckRow<Int>.
extension SelectableSection: ReactiveCompatible {}
extension Reactive where Base : SelectableSection<ListCheckRow<Int>> {
var selectedValue: Observable<Base.SelectableRow.Cell.Value?> {
return Observable.create { observer in
self.base.onSelectSelectableRow = {cell, row in
observer.onNext(row.value)
}
return Disposables.create {
observer.onCompleted()
}
}
}
}
This works fine and as I expected but when it comes to something more generic like the next code example, I get an error saying that: "Cannot assign to property: 'base' is a 'let' constant"
extension SelectableSection: ReactiveCompatible {}
extension Reactive where Base : SelectableSectionType {
var selectedValue: Observable<Base.SelectableRow.Cell.Value?> {
return Observable.create { observer in
self.base.onSelectSelectableRow = {cell, row in // Error: Cannot assign to property: 'base' is a 'let' constant
observer.onNext(row.value)
}
return Disposables.create {
observer.onCompleted()
}
}
}
}
Any help will be much appreciated, thanks. 🙏
The fundamental problem here is that SelectableSectionType is a protocol that isn't restricted to class types and Reactive assumes that Base is a class (or otherwise is not going to be modified by the observable creation.)
I think the most generic you can make this is something like:
extension Reactive {
func selectedValue<Row, T>() -> Observable<T?> where Base: SelectableSection<Row>, Row: SelectableRowType, T == Row.Cell.Value {
Observable.create { [base] observer in
base.onSelectSelectableRow = { cell, row in
observer.onNext(row.value) // this is problematic. See below.
}
return Disposables.create {
observer.onCompleted() // this is wrong. See below.
}
}
}
}
The biggest problem with the above though is that if you subscribe to the resulting Observable more than once or create more than one Observable using this computed property, all but the last subscription will silently fail. The simple way to fix this is to always remember to share any result but that's rather error prone.
The way to fix this would be to associate a Subject with each SelectableSection, but you can't modify the class, so what are we to do?
Here's a solution:
extension Reactive {
func selectedValue<Row, T>() -> Observable<T?> where Base: SelectableSection<Row>, Row: SelectableRowType, T == Row.Cell.Value {
Observable.create { [base] observer in
if let block = selectableSections.first(where: { $0.section === base }) {
let subject = block.subject as! PublishSubject<T?>
return Disposables.create(
block.disposable.retain(),
subject.subscribe(observer)
)
}
else {
let subject = PublishSubject<T?>()
let block = SelectableSectionBlock(
section: base,
subject: subject,
disposable: RefCountDisposable(disposable: Disposables.create {
selectableSections.removeAll(where: { $0.section === base })
})
)
base.onSelectSelectableRow = { cell, row in
subject.onNext(row.value)
}
selectableSections.append(block)
return Disposables.create(
block.disposable,
subject.subscribe(observer)
)
}
}
}
}
private struct SelectableSectionBlock {
let section: Section
let subject: Any
let disposable: RefCountDisposable
}
private var selectableSections = [SelectableSectionBlock]()
The selectableSections array stores a Subject and RefCountDisposable for each SelectableSection.
Whenever an Observable is created, or subscribed to...
if it's the first time working with this section, it will create a Subject and RefCountDisposable assign the onSelectSelectableRow to send a next event to the subject and store the subject in the array.
otherwise it will find the subject and disposable associated with this Section and retain the disposable.
Once it has the subject and disposable from above, it will subscribe the new observer to the subject and return a new Disposable that will remove that subscription and decrement the ref-count when the time comes.
Yes this is quite a bit more complex than the simple assignment case, but it's the right thing to do.
As for calling onCompleted() inside the disposable closure. By the time the closure is called, the observer has already emitted an onCompleted/onError event, or the observer has stopped listening to the observable. So this event will never be seen.
I've got a relationship where:
A Parent has many Children
ie:
class Factory: Object {
public let engines = List<Engine>()
}
class Engine:Object {
private let parents:LinkingObjects<Factory> = LinkingObjects(fromType: Factory.self, property: "engines")
var parent:Factory? {
return self.parents.first
}
}
I read the factories via JSON and create the children (Engine) manually in a for-loop, similar to this:
var engines:[Engine] = [Engine]()
for _ in stride(from:0, to: 3, by: 1) {
let engine: Engine = Engine.init()
engines.append(engine)
}
return engines
In my test I want to query the parent of a given engine to ensure that the parent is correct; or perhaps get a parent attribute.
However, whenever I try to grab an attribute via the parent its always empty;
for (_, element) in (factories.enumerated()) {
for (_, eng) in element.engines.enumerated() {
print (eng.parent ?? "N/A" as Any) // Always prints out N/A
}
}
Ideally I want to be able to access the parent's data; like the name of the parent, perhaps costs, etc.
I've tried resetting simulator and also deleting derived data; but regardless of what I do the results are always N/A or empty.
How can I query the given element and ensure that I can grab the parent data?
Many thanks
Turns out there were a number of issues that I had to do to resolve this.
I was using XCTest and Realm was causing issues where there were multiple targets.
Make all my model classes' public
Remove the models from the test target, this included a file where the JSON data was being loaded into memory
I had to write my data into Realm, which I had not done;
let realm = try! Realm()
try! realm.write {
for parent:EYLocomotive in objects {
for _ in stride(from:0, to: parent.qty, by: 1) {
let engine : EYEngine = EYEngine.init()
parent.engines.append(engine)
}
realm.add(parent)
}
}
Recently I have used ReSwift API, And I want to add ReSwiftRecorder too!
The sample of ReSwiftRecorder in Github is very simple app
I need to to something more complicated. I have an object which get data from server and I need to It reloads its data when app is not connected to net. Here is my code:
AppState:
struct AppState: StateType {
var menus: Result<[Menu]>?
}
MenuReducer:
func menusReducer(state: Result<[Menu]>?, action: Action) -> Result<[Menu]>? {
switch action {
case let action as SetMenusAction:
return action.menus
default:
return state
}
}
AppReducer:
struct AppReducer: Reducer {
func handleAction(action: Action, state: AppState?) -> AppState {
return AppState(
menus: menusReducer(state: state?.menus, action: action),
)
}
}
MenuActions:
struct SetMenus: Action {
let menus: Result<[Menu]>
}
I know I need to change MenuAction to Something like this:
let SetMenusActionTypeMap: TypeMap = [SetMenusAction.type: SetMenusAction.self]
struct SetMenusAction: StandardActionConvertible {
static let type = "SET_MENU_ACTION"
let menus: Result<[Menu]>
init() {}
init(_ standardAction: StandardAction) {}
func toStandardAction() -> StandardAction {
return StandardAction(type: SetMenusAction.type, payload: [:], isTypedAction: true)
}
}
but I got error on init functions
Return from initializer without initializing all stored properties
when I set a initializer code the error disappear but app does not restore saved data! How can I fix it?
You will want to add serialization/deserialization code. The menus property needs to be set. Also, you will want to serialize that property as payload:
let SetMenusActionTypeMap: TypeMap = [SetMenusAction.type: SetMenusAction.self]
struct SetMenusAction: StandardActionConvertible {
static let type = "SET_MENU_ACTION"
let menus: Result<[Menu]>
init() {
self.menus = // however you initialize that
}
init(_ standardAction: StandardAction) {
let maybeMenus = standardAction.payload["menus"] as? [Menu]?
self.menus = // create Result from Optional<[Menu]>
}
func toStandardAction() -> StandardAction {
let maybeMenus = self.menus.asOptional // Cannot serialize Result itself
return StandardAction(type: SetMenusAction.type, payload: ["menus" : maybeMenus], isTypedAction: true)
}
}
So problems I see here: JSON serialization depends on Dictionary representation of your payload data, i.e. the properties of your object. Can Result be serialized directly? I guess not, so you need to convert it, probably easiest to nil.
All in all, the payload is the key you missed and now you have to figure out how to use it with the data you have at hand. Also, it makes me a bit suspicious that the Result type itself is part of the AppState. I expected it to be reduced away or handled before dispatching an action, like SettingMenusFailedAction instead of ChangeMenusAction(result:) or similar. Just as a sidenote: actions should be more than typed property setters.
I have a method that should return Results, either by successfully querying, or by creating the records if they don't exist.
Something like:
class MyObject: Object {
dynamic var token = ""
static let realm = try! Realm()
class func findOrCreate(token token: String) -> Results<MyObject> {
// either it's found ...
let tokenResults = realm.objects(MyObject.self).filter("token = '\(token)'")
if !tokenResults.isEmpty {
return tokenResults
}
// ... or it's created
let newObject = MyObject()
newObject.token = token
try! realm.write {
realm.add(newObject)
}
// However, the next line results in the following error:
// 'Results<_>' cannot be constructed because it has no accessible initializers
return Results(newObject)
}
}
Maybe I should just be returning [MyObject] from this method. Is there any benefit to trying to keep it as Results instead of Array? I guess I'd lose any benefit of postponed evaluation since I'm already using isEmpty within the method, correct?
Results is an auto-updating view into underlying data in a Realm, which is why you can't construct it directly. So instead of return Results(newObject), you should return tokenResults, which will contain your newly added object, again because Results is an auto-updating view.
I have a Realm Object which has several relationships, anyone has a good code snippet that generalizes a copy method, to create a duplicate in the database.
In my case i just wanted to create an object and not persist it. so segiddins's solution didn't work for me.
Swift 3
To create a clone of user object in swift just use
let newUser = User(value: oldUser);
The new user object is not persisted.
You can use the following to create a shallow copy of your object, as long as it does not have a primary key:
realm.create(ObjectType.self, withValue: existingObject)
As of now, Dec 2020, there is no proper solution for 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 Dog")
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.
I had a similar issue and found a simple workaround to get a copy of a realm object. Basically you just need to make the object conform to the NSCopying protocol, something like:
import RealmSwift
import Realm
import ObjectMapper
class Original: Object, NSCopying{
dynamic var originalId = 0
dynamic var firstName = ""
dynamic var lastName = ""
override static func primaryKey() -> String? {
return "originalId"
}
init(originalId: Int, firstName: String, lastName: String){
super.init()
self.originalId = originalId
self.firstName = firstName
self.lastName = lastName
}
func copy(with zone: NSZone? = nil) -> Any {
let copy = Original(originalId: originalId, firstName: firstName, lastName: lastName)
return copy
}
}
then you just call the "copy()" method on the object:
class ViewController: UIViewController {
var original = Original()
override func viewDidLoad() {
super.viewDidLoad()
var myCopy = original.copy()
}
}
The nice thing about having a copy is that I can modify it without having to be in a realm write transaction. Useful when users are editing some data but didn't hit save yet or simply changed their mind.
Since this problem is still alive I post my solution which works but still needs to be improved.
I've created an extension of Object class that has this method duplicate that takes an object objOut and fills the flat properties by looking at self. When a non-flat property is found (aka a nested object) that one is skipped.
// Duplicate object with its flat properties
func duplicate(objOut: Object) -> Object {
// Mirror object type
let objectType: Mirror = Mirror(reflecting: self);
// Iterate on object properties
for child in objectType.children {
// Get label
let label = child.label!
// Handler for flat properties, skip complex objects
switch String(describing: type(of: child.value)) {
case "Double", "Int", "Int64", "String":
objOut.setValue(self.value(forKey: label)!, forKey: label)
break
default:
break
}
}
return objOut
}
Inside the Manager class for my Realms I have the method copyFromRealm() that I use to create my copies of objects.
To give you a practical example this is the structure of my Appointment class:
Appointment object
- flat properties
- one UpdateInfo object
- flat properties
- one AddressLocation object
- flat properties
- one Address object
- flat properties
- one Coordinates object
- flat properies
- a list of ExtraInfo
- each ExtraInfo object
- flat properties
This is how I've implemented the copyFromRealm() method:
// Creates copy out of realm
func copyFromRealm() -> Appointment {
// Duplicate base object properties
let cpAppointment = self.duplicate(objOut: Appointment()) as! Appointment
// Duplicate UIU object
cpAppointment.uiu = self.uiu?.duplicate(objOut: UpdateInfo()) as? UpdateInfo
// Duplicate AddressLocation object
let cpAddress = self.addressLocation?.address?.duplicate(objOut: Address()) as? Address
let cpCoordinates = self.addressLocation?.coordinates?.duplicate(objOut: Coordinates()) as? Coordinates
cpAppointment.addressLocation = self.addressLocation?.duplicate(objOut: AddressLocation()) as? AddressLocation
cpAppointment.addressLocation?.address = cpAddress
cpAppointment.addressLocation?.coordinates = cpCoordinates
// Duplicate each ExtraInfo
for other in self.others {
cpAppointment.others.append(other.duplicate(objOut: ExtraInfo()) as! ExtraInfo)
}
return cpAppointment
}
I wasn't able to find out a good and reasonable way to work with nested objects inside my duplicate() method. I thought of recursion but code complexity raised too much.
This is not optimal but works, if I'll find a way to manage also nested object I'll update this answer.
Swift 5+
Creates a Realm managed copy of an existing Realm managed object with ID
extension RLMObject {
func createManagedCopy(withID newID: String) -> RLMObject? {
let realmClass = type(of: self)
guard let realm = self.realm, let primaryKey = realmClass.primaryKey() else {
return nil
}
let shallowCopy = realmClass.init(value: self)
shallowCopy.setValue(newID, forKey: primaryKey)
do {
realm.beginWriteTransaction()
realm.add(shallowCopy)
try realm.commitWriteTransaction()
} catch {
return nil
}
return shallowCopy
}
}