ng-model在选择框上具有关联，而ng-repeat在选项上

Question

I have a Plunker here illustrating my issue . I have an object with an associated division . There is no division_id on the object, but in order to set or update the division I need to set the division_id field. Here's the sample object:

$scope.user = {
  name: "John",
  age: 32,
  division: {
    id: 3,
    name: "Alpha"
  }
};

And the example divisions:

$scope.divisions = [
  {
    name: "Gamma",
    id: 1
  },
  {
    name: "Alpha",
    id: 3
  },
  {
    name: "Beta",
    id: 5
  }
];

The way I'm building the select box is with ng-repeat , which I was hoping would bypass the need to track ng-model for the selected value.

    <div class="form-group">
      <label for="">Division</label>
      <select type="text" ng-model="user.division_id">
        <option ng-repeat="division in divisions"
          ng-selected="user.division.id == division.id">{{ division.name }}</option>
      </select>
    </div>

As you can see in the demo, the selected attribute is being placed on the right option, but still the select box display is blank. Even if I add division_id: 3 to the object, it continues to be blank. How can I get this to work without having to do a conversion on the object when loading and updating?

Edit: To address this question being flagged as a duplicate, I think this is unique because I'm asking how to build the select box with ng-repeat , not ng-options . Though the answer is similar to the answer for the proposed duplicate, I think other people might get stuck on this method and find it helpful to see the answer requires a different technique.

Answer 1

If you update your select as follows it will display by default to the users division.id.

<select ng-model="user.division" ng-options="d as d.name for d in divisions track by d.id">   

You seemed to be wanting to have a separate model division_id , the only reason I can think of for this is that you wanted to control the persistence of the user model when the selection is updated. If for some reason you want to intercept the end-users selection to the user model (or even just the in-memory user object) being updated then use a copy/there are many ways to do that, but it's not clear if that's what you're asking.

Updated plunkr

Note it would have worked to have kept the same option ng-repeat syntax, but this is the recommended angular way to deal with options.

Answer 2

As per your plunker, you need to remove the ng-model directive from the select tag for it to work.

if you need to set a division_id variable for your code, you can use ng-init.

<div class="form-group">
  <label for="">Division</label>
    <select type="text">
       <option ng-repeat="division in divisions"
          ng-selected="user.division.id == division.id"
          ng-init="division_id=division.name">{{ division.name }}
       </option>
      </select>
    </div>