player.swift

class Player : NSObject {
    var objectId: String?
    var teamName : NSString?
    var team :Team?
    var firstName : NSString?
    var lastName : NSString?
    
    //Inivitation.swift
    override func hostToKinveyPropertyMapping() -> [NSObject : AnyObject]! {
        return [
            "objectId" : KCSEntityKeyId,
            "teamName" : "teamName",
            "team" : "team",
            "firstName" : KCSUserAttributeGivenname,
            "lastName" :KCSUserAttributeSurname,
        ]
    }
    
    override class func kinveyPropertyToCollectionMapping() -> [NSObject : AnyObject]! {
        return [
            "team" : "Teams",
        ]
    }
    
    // Here you tell Kinvey which class to map the team property to. This
    // is how it knows how to build the object when it fetches it from the server.
    override class func kinveyObjectBuilderOptions() -> [NSObject : AnyObject]! {
        let referenceMap:[NSObject : AnyObject] = [
            "team" : Team.self
        ]
        return [
            KCS_REFERENCE_MAP_KEY : referenceMap
        ]
    }
}

savving.swift

    let store = KCSLinkedAppdataStore.storeWithOptions([
        KCSStoreKeyCollectionName : "Players",
        KCSStoreKeyCollectionTemplateClass : Player.self
        ])
    
    let player = Player()
    player.firstName = _username
    player.lastName = "Last Name"
    player.team = _team
    player.teamName = _team.name!
    
    store.saveObject(
        player,
        withCompletionBlock: { (objectsOrNil: [AnyObject]!, errorOrNil: NSError!) -> Void in
            if errorOrNil != nil {
                //save failed
                NSLog("Save failed, with error: %@", errorOrNil.localizedFailureReason!)
            } else {
                //save was successful
                NSLog("Successfully saved event (id='%@').", (objectsOrNil[0] as! NSObject).kinveyObjectId())
            }
        },
        withProgressBlock: nil
    )