angularjs - Accessibility of $index in ng-show -

i try displaying select when previous select checked.

<div ng-repeat="item in collection">  <div ng-show="$index === 0 || $parent.list[$index].nom">     <select ng-model="$parent.list[$index].nom" ng-options="..."></select> </div> 

1) <div ng-repeat="item in collection">

i loop through collection , create many selects there item in collection.

2) <div ng-show="$index === 0 || $parent.list[$index].nom">

i want display/hide parent div of selects 2 conditions :

1. i show div if index equal 0 (for display first select)
2. i show div if current ngmodel contains nom

3) <select ng-model="$parent.list[$index].nom" ng-options="...">

i put dynamic ngmodel each select has own model :

test exemple : have 3 options in select, want give opportunity member choose each option of select.

if member choose option of select 1 seconde select show on , if select option of second select third select show on no more else...

the probleme here : $index in directive ngshow seem's known condition :

$index === 0 

but no here :

$parent.list[$index].nom 

i think should be:

<div ng-show="$index === 0 || $parent.list[$index - 1].nom">     <select ng-model="$parent.list[$index].nom" ng-options="el el in els"></select> </div> 

note, want refer previous item in list, hence $index - 1.