Realm+CascadingDeletions

Realm+CascadingDeletions.swift

import Foundation
import RealmSwift

protocol CascadingDeletable {
    var cascadingDeletions: [AnyObject?] { get }
}

extension Realm {
    
    func delete<T: AnyObject>(cascading: List<T>) where T: CascadingDeletable {
        let o = cascading
        cascading.removeAll()
        delete(o)
    }
    
    func delete<T: AnyObject>(cascading: Results<T>) where T: CascadingDeletable {
        let o = cascading
        delete(o)
    }
    
    func delete<T: AnyObject>(cascading: [T]) where T: CascadingDeletable {
        for c in cascading {
            delete(c as! Object)
        }
    }
    
    func delete<T: AnyObject>(cascading: T) where T: Object, T: CascadingDeletable {
        
        for child in cascading.cascadingDeletions {
            if let object = child as? Object {
                delete(object)
            }
            if let cascade = child as? CascadingDeletable {
                delete(cascade as! Object)
            }
        }
        
        delete(cascading)
    }
}

Looks nice with extension methods!

But I am having trouble compiling it with Swift 3 and RealmSwift 1.1.0, but I receive the following error in line 11 and 15:
"Extra argument 'cascade' in call"

Do you know what could be wrong?

?

@Anders123f: I was able to compile by changing from objects.toArray() to Array(objects)

Hi
First, this extension looks very cool. Thanks for shared this
But, I found maybe you lost something.
If object is realmObject and CascadingDeletable, the object should be deleted too.
I add some code to the delete method:

 func delete<T: AnyObject>(_ object: T, cascade: Bool = true) where T: CascadingDeletable {
    ....
    if let object = object as? Object {
        delete(object)
    }
}

When I call delete(_:) in Swift, it is being dispatched to the original delete(_:) function on Realm, not the cascading one from your extension. Not sure how to make this work...

I would advise you not to use this solution.
Even after:

• adapting the code to Swift 3,
• fixing the algorithm with @orangeince answer
• adding some function definitions for the delete(_:, cascade:) method to be called for Object instance not conforming to the protocol

I've found issues with the fact that the method will not be called recursively, as let cascadingChild = child as? T will not work if the child is not the same type as its parent.

Removing this check and just using the child as a regular Object won't work either, as the where clause is not recognized if we do not pass a type that conforms to the type in its definition.

@AnthonyMDev - Realm provides initializers for an array of Realm Object<T>. The compiler can't infer the correct object type if you use .toArray().

func delete<T: AnyObject>(_ objects: List<T>, cascade: Bool = true) where T: CascadingDeletable {
    delete(Array(objects), cascade: cascade)
}

func delete<T: AnyObject>(_ objects: Results<T>, cascade: Bool = true) where T: CascadingDeletable {
    delete(Array(objects), cascade: cascade)
}

I tested this code today but it does not fullfill the requirements of a full cascading delete.

All my model classes are impelmenting the CascadingDeletable protocoll and are returning all childs that should be deleted in the cascadingDeletions array. Lets say you have the following structure:

Object A
   Sub 1
   Sub 2
      SubSub 2.1
      SubSub 2.2
   Sub 3
   ...

Sub 1, Sub 2, Sub 3 are getting deleted but SubSub 2.1, SubSub 2.2 and the Object A itself are not getting deleted with current Realm 2.4.0 version and your extensions. Tested on XCode 8 with Swift 3.0 and Realm 2.4.0.

Same issue here, I haven't been able to remove the a List attribute.

Any solutions to this?