why does changing self.view value affects all other tabs content

I have two tabs with different content. one of them shows some labels and buttons. and the other tab contain google map. in the second tab when I'm using this lines of code: (the last line of code)

let camera = GMSCameraPosition.cameraWithLatitude(lat1.doubleValue, longitude: lng1.doubleValue, zoom: 6)
let mapView = GMSMapView.mapWithFrame(CGRectZero, camera: camera)
mapView.myLocationEnabled = true
mapView.delegate = self
self.view = mapView

this affects the first tab content. and both tabs show googlemap. what should I do? (I'm using swift)

Can you show me some more codes about usage? Is self.view root view of child view controller or root view controller?

I've attached three .txt files which includes the codes of main view and two tabs (I just removed unnecessary lines of codes) in the file named: 'detailTab0.txt' I've written self.view = ... to show the googlemaps in that view. but it affects the other tab too. after tapping on tabs title it will show the correct content again but I want the correct content without any tapping!

main.txt detailTab1.txt detailTab0.txt