RealmSwift: Detach an object from Realm, including its properties of List type

Question

I want to create a duplicate of a persisted object such that the new instance has all the same values but is not attached to Realm. Using Object(value: persistedInstance) works great for classes whose properties are all strings, dates, numbers, etc. However, when duplicating an instance of a class with List type properties, the duplicate's List and the List's elements continue to reference the persisted records. How can I create a duplicate that's fully detached from Realm, including any Lists and elements in those Lists?

Answer 1

You can make a deep copy of your object via the following extension functions:

    import UIKit
    import Realm
    import RealmSwift
    
    protocol RealmListDetachable {

    func detached() -> Self
}

extension List: RealmListDetachable where Element: Object {

    func detached() -> List<Element> {
        let detached = self.detached
        let result = List<Element>()
        result.append(objectsIn: detached)
        return result
    }

}

@objc extension Object {

    public func detached() -> Self {
        let detached = type(of: self).init()
        for property in objectSchema.properties {
            guard
                property != objectSchema.primaryKeyProperty,
                let value = value(forKey: property.name)
            else { continue }
            if let detachable = value as? Object {
                detached.setValue(detachable.detached(), forKey: property.name)
            } else if let list = value as? RealmListDetachable {
                detached.setValue(list.detached(), forKey: property.name)
            } else {
                detached.setValue(value, forKey: property.name)
            }
        }
        return detached
    }
}

extension Sequence where Iterator.Element: Object {

    public var detached: [Element] {
        return self.map({ $0.detached() })
    }

}

Use

/// in collections
let data = realm.objects(AbcDfg.self).detached

/// single object
data.first?.detached()

Answer 2

This is not yet supported natively by Realm, but a requested feature tracked by issue #3381.

For now, you would need to implement your own deep copy constructor. A common strategy is to do that on every model and call the deep copy constructors of related objects. You need to pay attention though that you don't run into cycles.