ios 7 view with transparent content overlaps previous view

I did this.

-(void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    [self.view setAlpha:0];
}

Do not forget re set alpha when come back.

- (void) viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [self.view setAlpha:1];
}