xcode 上 A -> navB -> B，A弹出的modal视图B需要显示导航栏，于是B embed 一个navigationController navB，这样A 需要传值给B时中间隔了一个navB

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- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqualToString:@"0"]) {
        UINavigationController * nav = segue.destinationViewController;
        LaunchTongChengTableViewController * vc = (LaunchTongChengTableViewController *)nav.topViewController;
        if ([vc respondsToSelector:@selector(setScenarioType:)]) {
            vc.scenarioType = 0;
        }
    }
}