AngularJs: Add class based on Model

Just trying to apply a class if something is true. The documentation is very brief on http://docs.angularjs.org/api/ng.directive:ngClass

Trying to add a class of favorite on the li if 1 === true

Here's my Mock Object

    $scope.restaurantListFromSearch = [
        {restaurantName: "Zocala",
        details: {
            image: "http://placehold.it/124x78",
            url: "#",
            cuisineType: ["Sandwiches", "American", "BBQ"],
            description: "Modern, healthy, awesome BBW",
            priceRange: "$",
            userFavorite: 0
        }},
        {restaurantName: "Subway",
        details: {
            image: "http://placehold.it/124x78",
            url: "#",
            cuisineType: ["Sandwiches", "American", "BBQ"],
            description: "Modern, healthy, awesome BBW",
            priceRange: "$",
            userFavorite: 1
        }},
        {restaurantName: "Hungry Howies",
        details: {
            image: "http://placehold.it/124x78",
            url: "#",
            cuisineType: ["Sandwiches", "American", "BBQ"],
            description: "Modern, healthy, awesome BBW",
            priceRange: "$",
            userFavorite: 0
        }}                      
    ];

And here's my markup.

        <ul>
            <li ng-repeat="restaurant in restaurantListFromSearch" ng-class="{restaurant.details.userFavorite === 1: favorite}">
                <img src="{{restaurant.details.image}}" alt="{{restaurant.restaurantName}}">

                <div class="details">
                    <a href="{{restaurant.details.url}}">{{restaurant.restaurantName}}</a>
                    <span class="cuisine-type">{{restaurant.details.cuisineType}}</span>
                    <p>{{restaurant.details.description}}</p>