Angular ng-repeat Error "Duplicates in a repeater are not allowed."

Question

I am defining a custom filter like so:

<div class="idea item" ng-repeat="item in items" isoatom>    
    <div class="section comment clearfix" ng-repeat="comment in item.comments | range:1:2">
        ....
    </div>
</div>

As you can see the ng-repeat where the filter is being used is nested within another ng-repeat

The filter is defined like this:

myapp.filter('range', function() {
    return function(input, min, max) {
        min = parseInt(min); //Make string input int
        max = parseInt(max);
        for (var i=min; i<max; i++)
            input.push(i);
        return input;
    };
});

I'm getting:

Error: Duplicates in a repeater are not allowed. Repeater: comment in item.comments | range:1:2 ngRepeatAction@https://ajax.googleapis.com/ajax/libs/angularjs/1.1.4/an

Answer 1

The solution is actually described here: http://www.anujgakhar.com/2013/06/15/duplicates-in-a-repeater-are-not-allowed-in-angularjs/

AngularJS does not allow duplicates in a ng-repeat directive. This means if you are trying to do the following, you will get an error.

// This code throws the error "Duplicates in a repeater are not allowed.
// Repeater: row in [1,1,1] key: number:1"
<div ng-repeat="row in [1,1,1]">

However, changing the above code slightly to define an index to determine uniqueness as below will get it working again.

// This will work
<div ng-repeat="row in [1,1,1] track by $index">

Official docs are here: https://docs.angularjs.org/error/ngRepeat/dupes