Javascript 将select插入数组角度模式窗体

我试图创建一个数组，其中每个元素都包含select。我现在的代码：

angular.module('MaterialAidForm', ['schemaForm']).controller('FormController', function($scope) {
$scope.schema = {
  "type": "object",
  "title": "Comment",
  "required": [
    "comments"
  ],
  "properties": {
    "comments": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
            "spam": {
                "title": "Spam",
                "type": "select",
                "titleMap":
                {
                    "a": "A",
                    "b": "B"
                }
            }            
        },
        "required": [
          "name",
          "comment"
        ]
      }
    }
  }
};

$scope.form = ["*"];
$scope.model = {};
});

但当我打开浏览器时，我只看到里面没有选择器的数组