the tab bar isn't showed

Hi everybody,

I have a problem on Xcode 7, with an iPhone project.

I am trying to build an app with a tab bar. In one of the items I want to have buttons, who pushed they show you a different view. After the navigation in the different view controller, if if you push a button you return to the previous view controller. But here is the problem: if you return to the first tab bar controller by the buttons, the tab bar isn't showed. Can somebody help me, please?

Thanks a lot!