javascript - 带有4个选择选项的Angularjs链式选择在更改时为空

Question

我有以下问题：当我使用例如 4 个选择实现链式选择并更新第二个选择时，第三个选择为空，但第四个保留该值。这是 jsfiddle 的链接，其中包含我用来进行链式选择的策略（这个小提琴不是我做的！）：

http://jsfiddle.net/pythondave/JUZDf/

1. 选择老爷车
2. 选择 1948 年保时捷 356-A 跑车
3. 选择颜色
4. 选择红色
5. 选择 1949 年捷豹 XK 120

现在你看到第四个选择没有变空你怎么能让那个为空？

HTML部分：

<div ng-app ng-controller="SelectController">
 <select ng-model="category" ng-options="c.name for c in sampleProductCategories">    </select>
 <select ng-model="categoryItem" ng-options="p.name for p in category.products"></select>
 <select ng-model="subChild" ng-options="o.value for o in categoryItem.options"></select>
 <select ng-model="level4" ng-options="o.value for o in subChild.options"></select>

  <hr />
  category={{category.name}}<br/>
  product={{categoryItem.name}}<br/>
  subChild={{subChild.value}}<br/>
  level4={{level4.value}}<br/>

</div>

Javascript：

function SelectController($scope) {
    // Data taken from KnockoutJs cart example
    $scope.sampleProductCategories = [
      {
        "name": "Classic Cars",
          "products": [
          {
            "name": "1948 Porsche 356-A Roadster",
              "options":[
                  {"value": "Color",
                   "options":[
                  {"value": "Red"},
                  {"value":"Black"}
                  ],                                    
               },
                  {"value":"Seats",
                  "options":[
                  {"value": "Leather"},
                  {"value":"Cloth"}
                  ],    

                  },

                 {"value":"Warranty",
                  "options":[
                  {"value": "2 Year"},
                  {"value":"3 Year"}
                  ],    

                  } 

              ],
            "price": 53.9
          },
          {
            "name": "1948 Porsche Type 356 Roadster",
            "price": 62.16
          },
          {
            "name": "1949 Jaguar XK 120",
            "price": 47.25
          }
        ]

      },
      {
        "name": "Motorcycles",
        "products": [
          {
            "name": "1936 Harley Davidson El Knucklehead",
            "price": 24.23
          },
          {
            "name": "1957 Vespa GS150",
            "price": 32.95
          },
          {
            "name": "1960 BSA Gold Star DBD34",
            "price": 37.32
          }
        ]

      },
      {
        "name": "Planes",
          "products": [
          {
            "name": "1900s Vintage Bi-Plane",
            "price": 34.25
          },
          {
            "name": "1900s Vintage Tri-Plane",
            "price": 36.23
          },
          {
            "name": "1928 British Royal Navy Airplane",
            "price": 66.74
          },
          {
            "name": "1980s Black Hawk Helicopter",
            "price": 77.27
          },
          {
            "name": "ATA: B757-300",
            "price": 59.33
          }
        ]

      }
    ];
}

Answer 1

When a new select value is being selected it is only changing the model variable linked to that select box, the remainder are unchanged. 因此，尽管为 选择了一个新值categoryItem，subChild但仍会从之前选择的任何内容中保留其值，并且第四个选择框正是从该值构建它的选项，从而保留了这些值。使用前 3 个选择框中的任何一个时，您将看到相同的结果。

您可以使用该ng-change指令在选择框更改上执行函数以重置所需的范围变量：

<select ng-model="category" ng-change="update(select1)" ng-options="c.name for c in sampleProductCategories">    </select>
<select ng-model="categoryItem" ng-change="update(select2)" ng-options="p.name for p in category.products"></select>

然后在你的控制器中：

function SelectController($scope) {
    $scope.update = function (select) {
        // update the appropriate n-selectBoxNum scope variables here
    }
}