present一个半透明的ViewController的方法

RecommandViewController *recommandVC = [[RecommandViewController alloc]init];
    if([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0){
        recommandVC.modalPresentationStyle=
        UIModalPresentationOverCurrentContext|UIModalPresentationFullScreen;//if the controller has container like navigationcontroller or tababr controlelr,if you don`t use the UIModalPresentationFullScreen the bar will cover the viewcontroller
        [FindAppDelegate().window.rootViewController presentViewController:recommandVC animated:NO completion:^{
            recommandVC.view.backgroundColor=[UIColor clearColor];//you can figure any transparent here
        }];
    }else{
        FindAppDelegate().window.rootViewController.modalPresentationStyle=
        UIModalPresentationCurrentContext|UIModalPresentationFullScreen;//you must use the rootViewController if the system version under the iso 8.0 or the background will be black
        [FindAppDelegate().window.rootViewController presentViewController:recommandVC animated:YES completion:^{
            recommandVC.view.backgroundColor=[UIColor clearColor];
        }];
    }

vc.modalPresentationStyle = UIModalPresentationCustom;