ios - Thread 1: EXC_BAD_ACCESS (code=2, address=0x7fff59d8dff8) -

what i'm trying do:

the following bit of code 2 buttons on page. page part of array of pages (which stored in self.parent; stores index has in said array in self.index). 2 buttons used navigate forwards , backwards in array of pages. if tries go forward hits end of array, should go first page; likewise going , hitting beginning of array.

@ibaction func previousbutton(sender: anyobject) {      self.prev() }  @ibaction func nextbutton(sender: anyobject) {      self.next() }  func next(){      if let _parent = self.parent{          if self.index != _parent.getsize()-1 {              self.view.addsubview(_parent[self.index+1].view)         }         else{              self.view.addsubview(_parent[0].view)         }     }     else{         println("this page not part of list")     } }  func prev(){      if let _parent = self.parent{          if self.index != 0 {              self.view.addsubview(_parent[self.index-1].view)         }         else{             self.view.addsubview(_parent[_parent.getsize()-1].view)         }     }     else{         println("this page not part of list")     } } 

problem is:

edit: crashes have nothing if statements , isn't random either; crashes when hit next button tenth time, previous button tenth time (ten number of pages have in list; if add more pages, number changes accordingly), , when press prev after pressing next or pressing next after pressing next.

i figured out problem: not switching between pages, adding 1 on top of others; crash occurs when attempt show page loaded (and still somewhere beneath stack of pages).

now need find better way switch between them.