javascript - 有没有办法在 AngularJs 中只投赞成票或反对票一次？

Question

以下代码取自 Code Academy 的 AngularJS 类(class)。在第一课中，向用户提供了“喜欢”或“不喜欢”的评级选项。一旦用户点击“喜欢”按钮，投票就会上升，同样，用户点击“不喜欢”按钮，投票就会增加到减号。但是代码中没有办法限制用户只能投赞成票或反对票一次。有没有办法使用 AngularJS 限制用户投票一次？

html代码

<div class="rating">
        <p class="likes" ng-click="plusOne($index)">+{{product.likes}}</p>
        <p class="dislikes" ng-click="minusOne($index)">-{{product.dislikes}}</p>
</div>

AngularJS 代码

app.controller('MainController', ['$scope',
  function($scope) {
    $scope.title = 'Top Sellers in Books in this Great City';
    $scope.promo = 'Our Christmas Promo is on the way!';
    $scope.products = [{
      name: 'The Book of Trees',
      price: 19,
      pubdate: new Date('2014', '03', '08'),
      cover: 'img/the-book-of-trees.jpg',
      likes: 0,
      dislikes: 0
    }, {
      name: 'Program or be Programmed',
      price: 8,
      pubdate: new Date('2013', '08', '01'),
      cover: 'img/program-or-be-programmed.jpg',
      likes: 0,
      dislikes: 0
    }, {
      name: 'Book1',
      price: 8,
      pubdate: new Date('2015', '04', '02'),
      cover: 'img/..',
      likes: 0,
      dislikes: 0
    }, {
      name: 'Book2',
      price: 8,
      pubdate: new Date('2015', '09', '09'),
      cover: 'img/..',
      likes: 0,
      dislikes: 0
    }];
    $scope.plusOne = function(index) {
      $scope.products[index].likes += 1;
    };
    $scope.minusOne = function(index) {
      $scope.products[index].dislikes += 1;
    };
  }
]);

Answer 1

是的，只需标记数组中的对象即可。

$scope.plusOne = function(index) {
    if(!$scope.products[index].upvoted){
      $scope.products[index].likes += 1;
      $scope.products[index].upvoted = true;
    }
};
$scope.minusOne = function(index) {
    if(!$scope.products[index].downvoted){
      $scope.products[index].dislikes += 1;
      $scope.products[index].downvoted = true;
    }
};

如果您希望通过赞成票来否定反对票(反之亦然)，则必须添加更多内容，但这很简单。