gistfile1.txt

DBPageViewController * pc = [self getPageController:a.toPageId];
        pc.refer = pid;
        [self addChildViewController:pc];
        [self.view addSubview:pc.view];

        CGFloat width = self.view.frame.size.width;
        CGFloat height = self.view.frame.size.height;
        pc.view.frame = CGRectMake(width, 0, width, height);
        
        DBPageViewController * pfc = [self getPageController:a.fromPageId];
        __weak id weakSelf = self;
        [self transitionFromViewController:pfc
                          toViewController:pc duration:0.4
                                   options:UIViewAnimationOptionTransitionNone
                                animations:^{
                                    pfc.view.frame = CGRectMake(0 - width, 0, width, height);
                                    pc.view.frame = CGRectMake(0, 0, width, height);
                                }
                                completion:^(BOOL finished){
                                    pfc.view.frame = CGRectMake(0, 0, width, height);
                                    [pc didMoveToParentViewController:weakSelf];
                                    [self print];
                                }];