ios - how to call tab bar view controller by click button function in swift -

i have 1 common tab bar view controller.and have connected 3 other view controllers navigation bar , connect 3 view controllers main tab bar view controller.so have 3 tab bar items 3 view controller.

that 1.home 2. cart 3. feedback

this fine !!

and first view controller(that first tab bar view controller) have table view data , detail view controller.and in detail view controller have 1 button called "go cart".

so actual flows when user press go cart.it have move cart` view controller.now moving.

but problem .i not able see tab bar items , other items .but if go normal each tab bar items showing tab bar items.

when go detail view button click cart tab bar view controller..then no tab bar items showing down.

i did demo prototype.like drag button cart tab bar view controller navigation bar.

but not showing tab bar why.please me out.i don't have single solution solve this.i using swift 2.2.

thanks.

updated :

so need code thing right?.but don't know how handle code:

 let barviewcontrollers = sender.destinationviewcontroller as! uitabbarcontroller      let nav = barviewcontrollers.viewcontrollers![1] as! uinavigationcontroller      let destinationviewcontroller = nav.topviewcontroller as! cartvc 

but getting crash in first line :

fatal error: unexpectedly found nil while unwrapping optional value (lldb)  

please me out

here storyboard similar yours.

now remove segue button "go cart" similar "show second tab" button in storyboard

instead provide action follows,

 @ibaction func showsecondtab(sender: anyobject) {             let  navcontroller = self.tabbarcontroller?.viewcontrollers![1] as! uinavigationcontroller             ///secondviewcontroller in case cart             let secondviewcontroller = navcontroller.viewcontrollers[0] as! secondviewcontroller             //set values want pass             //lets want pass name secondvc             secondviewcontroller.name = "abcd"              self.tabbarcontroller?.selectedindex = 1     } 

you can print , check values in viewdidload of secondvc(cartvc).