Realm Cascade Deletion in Swift

RealmCascadeDeletion.swift

import RealmSwift
import Realm

protocol CascadeDeleting {
    func delete<S: Sequence>(_ objects: S, cascading: Bool) where S.Iterator.Element: Object
    func delete<Entity: Object>(_ entity: Entity, cascading: Bool)
}

extension Realm: CascadeDeleting {
    func delete<S: Sequence>(_ objects: S, cascading: Bool) where S.Iterator.Element: Object {
        for obj in objects {
            delete(obj, cascading: cascading)
        }
    }
    
    func delete<Entity: Object>(_ entity: Entity, cascading: Bool) {
        if cascading {
            cascadeDelete(entity)
        } else {
            delete(entity)
        }
    }
}

private extension Realm {
    private func cascadeDelete(_ entity: RLMObjectBase) {
        guard let entity = entity as? Object else { return }
        var toBeDeleted = Set<RLMObjectBase>()
        toBeDeleted.insert(entity)
        while !toBeDeleted.isEmpty {
            guard let element = toBeDeleted.removeFirst() as? Object,
                !element.isInvalidated else { continue }
            resolve(element: element, toBeDeleted: &toBeDeleted)
        }
    }
    
    private func resolve(element: Object, toBeDeleted: inout Set<RLMObjectBase>) {
        element.objectSchema.properties.forEach {
            guard let value = element.value(forKey: $0.name) else { return }
            if let entity = value as? RLMObjectBase {
                toBeDeleted.insert(entity)
            } else if let list = value as? RLMSwiftCollectionBase {
                for index in 0..<list._rlmCollection.count {
                    if let entity = list._rlmCollection.object(at: index) as? RLMObjectBase {
                        toBeDeleted.insert(entity)
                    }
                }
            }
        }
        delete(element)
    }
}

Probably won't fix all the situations, but you can solve some of the issue by using Embedded Objects.

Realm Uses Cascading Deletes for Embedded Objects
When you delete a Realm object, Realm automatically deletes any embedded objects referenced by that object. Any objects that your application must persist after the deletion of their parent object should use relationships instead.

I haven't used Realm for a while now. but I can point to the right place in Realm Docs
Two things come to my mind trying RealmSwift.List instead RealmSwift.ListBase
And cleaning your derived data folder from Xcode.
Again these are only some ideas to go forward. I haven't tried them.

@jhoanarango @niralishaha25 as mentioned before, you can use Embedded Objects for automated cascade deleting. But if you still want to use the snippet on realm v10+, that should work as follows:

private func resolve(element: Object, toBeDeleted: inout Set<RLMObjectBase>) {
    element.objectSchema.properties.forEach {
        guard let value = element.value(forKey: $0.name) else { return }
        if let entity = value as? RLMObjectBase {
            toBeDeleted.insert(entity)
        } else if let list = value as? RLMSwiftCollectionBase {
            for index in 0..<list._rlmCollection.count {
                if let entity = list._rlmCollection.object(at: index) as? RLMObjectBase {
                    toBeDeleted.insert(entity)
                }
            }
        }
    }
    delete(element)
}

@aleyooop Thanks for your input. I've updated the Gist with your suggestion.