Error: [ngRepeat:dupes] what does this mean? - duplicates

Question

repeat directive outputing wine records from an api. I have a factory function to serve up the wine API which is then accessed in my controller
app.factory("Wine", function ($http){
var factory = {};
//getWines
factory.getWines = function(){
return $http.get("http://www.greatwines.9000.com")
}
}
Controller:
app.controller("winesCtrl", function($scope, $http, Wine){
Wine.getWines()
.success(function(wines){
$scope.wines = wines;
})
.error(function(){
alert("Error!");
});
});
VIEW:
<h2>Wine list</h2>
<div class="row margin-top-20 wine-container" ng-repeat="wine in wines">
<div class="col-sm-3">
<img src="{{wine.picture}}" class="img-responsive" />
</div>
<div class="col-sm-9">
<div class="margin-top-20">
<span class="bold">Name: </span><span>{{wine.name}}</span>
</div>
<div>
<span class="bold">Year: </span><span>{{wine.year}}</span>
</div>
<div>
<span class="bold">Grapes: </span><span>{{wine.grapes}}</span>
</div>
<div>
<span class="bold">Country: </span><span>{{wine.country}}</span>
</div>
<div>
<span class="bold">Region: </span><span>{{wine.region}}</span>
</div>
<div>
<span class="bold">Price: </span><span>{{wine.price}}</span>
</div>
<div>
<span class="bold">{{wine.description}}</span>
</div>
<div class="margin-top-20">
Edit Wine
</div>
</div>
</div>
I clicked on this error and in typical "vague" angularjs fashion I get this:
Duplicates in a repeater are not allowed. Use 'track by' expression to specify unique keys. Repeater: wine in wines, Duplicate key: string:e, Duplicate value: e
What does this mean? wine is not the same as "wines" so why does it think it is a duplicate?

Answer 1

It is true that AngularJS uses keys to associate DOM nodes with items. So, you can solve by adding "track by $index".
It will look like this
ng-repeat="wine in wines track by $index"

Answer 2

Occurs if there are duplicate keys in an ngRepeat expression. Duplicate keys are banned because AngularJS uses keys to associate DOM nodes with items.
This means that $scope.wines have some values which are duplicate.
You can also refer this post : Angular ng-repeat Error "Duplicates in a repeater are not allowed."