Realm - How to get a list of on owners of an entity in a parent-child relationship?

Question

Using Swift Realm, I'm wanting to get of owners of a child from the viewpoint of the parent.

In simple terms, the entity relationship can be described as:

Parent -< Child <- Player

Using a given Parent, I want to get a list of Players (owners).

I believe my query is wrong, when I try my query;

// Cut-down summary of Realm objects and relationships
public class Parent: Object {
  var children = List<Child>()
}
public class Child: Object {
  private let parents = LinkingObjects(fromType: Parent.self, property: "children")
  private let owners = LinkingObjects(fromType: Player.self, property: "children")
  var parent:Parent? {
      return self.parents.first
  }
  var owner: Player? {
      return self.owners.first
  }
}
public class Player : Object {
  public let children = List<Child>()
}



let realm = try! Realm()
self.createPlayers(amount: 5)
let playerList = realm.objects(EYPlayer.self)
XCTAssert(playerList.count == 5)


// In my tests:
let firstParent = realm.objects(Parent.self).first
let firstChild = firstParent?.children.first
let firstPlayer = realm.objects(Player.self).first

// Assign the first player with the first child
try! realm.write {
    firstPlayer?.children.append(firstChild!)
}

// give me a list of owners for a given parent
let owners = realm.objects(Parent.self).filter("ANY children.owners.@count > 0")
print (owners)

// Test fails; it says there are 0 results
XCTAssert(owners.count == 1, "Expected: 1, Found: \(owners.count)")

This test fails:

XCTAssert(owners.count == 1, "Expected: 1, Found: \(owners.count)")

I expect there to be 1 owner.

But instead, I get 0 owners.

What am I doing wrong?

How can I get a list of owners of a given child using NSPredicates and Realm?

Many thanks

Edit: Found that i wasn't adding any players; a summarized version of adding players is shown above

Answer 1

I have now solved the issue.

1. There was no player data to append the child to; I've fixed this in my xctests

2. After I did this, and a few adjustments to my tests, the queries appear to be working and verified it in my logger output.

       let firstParent = realm.objects(Parent.self).first
       let firstPlayer = realm.objects(Player.self).first
       let firstChild = firstParent?.children.first
   
       XCTAssert(firstChild?.parent == firstParent)
   
       try! realm.write {
           firstPlayer!.children.append(firstChild!)
       }
   
       let listOfChildren = realm.objects(Parent.self).filter("ANY children.owners.@count > 0")
       XCTAssert(listOfChildren.count == 1)
       XCTAssert(firstPlayer?.children.count == 1)
   
       for child in listOfChildren {
           for (index, eng) in child.children.enumerated() {
               if (index == 0) {
                   XCTAssert(eng.owner != nil)
               }
               XCTAssert(child.parent == loco)
           }
       }
   

The tests pass, and through some console logs I was able to verify my expectations.

Issue is resolved.

Closed.