ios - "Back" button is missing in my navigation controntroller -

• i create standard navigation controller
• i editor > "embed in" navigation controller
• i create segue mother controller navigation controller, name it

• i perform custom segue:

  performseguewithidentifier(constants.seguelistmessagestomessages, sender:view)

great, pops up.

however, child view doesn't have button on navigation controller bar.

i guess add bar button item...but can't find chevron apple uses "back" in symbols. why can't button there automatically?

embed mother controller in navigation controller create segue link. [navigation controller] <-(relationship segue)-> [root view controller] -(show segue)-> [child view controller]