dispatch_group_bug.swift

let group = dispatch_group_create()
        
        dispatch_group_enter(group)
        self.analyticCrawler.fetchLikes { (succeeded, likes) -> (Void) in
            if succeeded {
                self.likes = likes
            } else {
                self.likes = []
            }
            dispatch_group_leave(group)
        }

        dispatch_group_enter(group)
        self.analyticCrawler.fetchComments { (succeeded, comments) -> (Void) in
            if succeeded {
                self.comments = comments
            } else {
                self.comments = []
            }
            dispatch_group_leave(group)
        }
        
        
        
        dispatch_group_notify(group, dispatch_get_main_queue()) {
            var userInteractions : [String : UserInteraction] = Dictionary<String, UserInteraction>()
            
            for like in self.likes! {
                if let userInteraction = userInteractions[like.userSummary.username] {
                    userInteraction.addLike(like)
                } else {
                    let userInteraction = UserInteraction(userSummary: like.userSummary)
                    userInteraction.addLike(like)
                    userInteractions[like.userSummary.username] = userInteraction
                }
            }

            for comment in self.comments! {
                if let from = comment.from {
                    if let userInteraction = userInteractions[from.username] {
                        userInteraction.addComment(comment)
                    } else {
                        let userInteraction = UserInteraction(userSummary: from)
                        userInteraction.addComment(comment)
                        userInteractions[from.username] = userInteraction
                    }

                }
            }
            
            self.userInteractions = Array(userInteractions.values)
            completion(true)
        }