MVC

model.swift

    class func loadMessage(complete: (_ objects: Any, error: Error?) -> Void) {
        let managerQuery = UserModel.query()!
        
        let userRole = PFRole(withoutDataWithObjectId: "lEGrVrXO0a")  // 角色：球場管理
        managerQuery.whereKey("userRole", equalTo: userRole)
        
        let caddy = UserModel.current()!
        let courseID = caddy.course!
        managerQuery.whereKey("course", equalTo: courseID)
        
        managerQuery.findObjectsInBackground(block: { (objects, error) in
            let manager = objects!.first as! UserModel
            
            let sendQuery = iPadMessageTable.query()!
            sendQuery.whereKey("sender", equalTo: caddy)
            sendQuery.whereKey("receiver", equalTo: manager)
            
            let receiverQuery = iPadMessageTable.query()!
            receiverQuery.whereKey("sender", equalTo: manager)
            receiverQuery.whereKey("receiver", equalTo: caddy)
            
            let mainQuery = PFQuery.orQuery(withSubqueries: [sendQuery, receiverQuery])
            mainQuery.order(byAscending: "createdAt")
            mainQuery.whereKey("createdAt", greaterThan: GolfaceUtility.dateAtBeginningOfDay(for: Date()))
            mainQuery.findObjectsInBackground { (objects, error) in
                complete(objects, error)
            }
        })
    }

observer.swift

        NotificationCenter.default.addObserver(forName: Notification.Name(rawValue: "MessageLoadSuccess"), object: nil, queue: nil, using: { [unowned self] (notification) in
            self.messages = [JSQMessage]()
            
            for object in notification.object as! [iPadMessageTable] {
                let senderID = object.sender!.objectId
                let currentID = UserModel.current()!.objectId
                let sendID = (senderID == currentID) ? self.user1.id : self.user2.id;
                
                self.messages.append(JSQMessage(senderId: sendID, displayName: "", text: object.message))
            }
            
            self.collectionView.reloadData()
            self.scrollToBottom(animated: false)
            
            self.progressDelegate.hideProgressView()
            
            for object in notification.object as! [iPadMessageTable] {
                if object.read == false {
                    object.read = true
                    object.saveEventually()
                }
            }
        })