Calling AngularJS service methods in all views

I am having the below index.html page which has the main content and other views are called inside ion-nav-view directive based on the ionic route.

<body ng-app="index">

<ion-nav-bar class="bar-stable" align-title="center">

    <ion-nav-back-button>
    </ion-nav-back-button>

    <ion-nav-buttons side="left">
        <button class="button" ui-sref="index.view">
            Home
        </button>
    </ion-nav-buttons>

    <ion-nav-buttons side="right">
        <button class="button" ng-click="showPopOver($event)">
            Menu
        </button>
    </ion-nav-buttons>

</ion-nav-bar>

<ion-nav-view></ion-nav-view>

</body>

In my service, I have a method called showPopOver() and I want this to be called in all views as it contains some reusable code.

But I am not able to call the service method in my view. How should I modify my code to enable this?