Obtain the key's name from the select query

My task is to populate a select element from JSON data, but the challenge lies in the formatting of the JSON where the keys contain important information. I do not have control over how the data is structured.

I am attempting to iterate through the JSON and extract the key names for the main objects within the array. However, due to it being an object, I am unable to simply retrieve its name - Object.keys() does not work as expected within ng-options due to scoping issues.

I have tried various approaches similar to the following code snippet without success:

<select ng-model="$ctrl.vals"
        ng-options="val as key for (key, val) in $ctrl.data"
        ng-change="$ctrl.onChange()" name="{{$ctrl.name}}"
        size="{{$ctrl.data.length}}" multiple>
</select>

The above code returns "0" because it is formatted as 0: [object object]. The closest result I achieved was getting [Object Object] returned, but my goal is to retrieve the key of that object, which has proven challenging.

An example of the data format I'm dealing with is:

{
"Games": [{
    "Name": "Warhammer 40k 8th Edition",
    "Factions": [{
        "Space Marines": {
            "Units": [{
                "Name": "Primaris Space Marine Captain",
                "Number": 1,
                "Cost": -1,
                "Ability": "When captain enters play you win",
                "AddOns": [{
                    "Name": "My AddOn",
                    "Cost": 0,
                    "Text": "Add an extra Captain",
                    "IsSelected": false
                }],
                "Gear": [{
                    "Name": "Frag Grenade",
                    "Cost": 0
                }]

            }]
        }
        }]
    }]
}

Within the given JSON context above, my objective is to include Factions and display the text "Space Marines" as an option. What could I be overlooking?

Answer №1

If the reference to $ctrl.data in your code pertains to the value of the "Factions" property, then the ng-options syntax you are using is not suitable (specifically, the ... for (key, value) in ... structure necessitates $ctrl.data to be an object, which it is not).

Therefore, it would be advisable to utilize the array format for ng-options, allowing you to include extra functions that can extract the label and model associated with a selected option.

Here is a possible implementation:

angular
  .module('app', [])
  .controller('ctrl', function () {
    const $ctrl = this;
    $ctrl.modelFor = function (obj) {
      const [key] = Object.keys(obj);
      return key ? obj[key] : null;
    };
    $ctrl.labelFor = function (obj) {
      const [key] = Object.keys(obj);
      return key;
    };
    $ctrl.data = [{
      "Space Marines": {
        "Units": [{
          "Name": "Primaris Space Marine Captain",
          "Number": 1,
          "Cost": -1,
          "Ability": "When captain enters play you win",
          "AddOns": [{
            "Name": "My AddOn",
            "Cost": 0,
            "Text": "Add an extra Captain",
            "IsSelected": false
          }],
          "Gear": [{
            "Name": "Frag Grenade",
            "Cost": 0
          }]
        }]
      }
    }];
  });
<div
  ng-app="app"
  ng-controller="ctrl as $ctrl">
  <select
    ng-model="$ctrl.vals"
    ng-options="$ctrl.modelFor(obj) as $ctrl.labelFor(obj) for obj in $ctrl.data"></select>
  <pre>{{ $ctrl.vals }}</pre>
</div>
<script src="https://unpkg.com/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e2838c85978e8390a2d3ccd5ccda">[email protected]</a>/angular.min.js"></script>

Additionally, it appears that your data structure may need some revision. If each element within $ctrl.data can contain multiple keys, note that this method will pick just the first one arbitrarily (therefore, the order is not guaranteed when iterating through keys).

Answer №2

Modify the information:

 $ctrl.mapped = $ctrl.data.map(_ => {
     var entry = Object.entries(_)[0];
     return { key: entry[0], value: entry[1] };
 });

Implement it in the HTML structure:

<select ng-model="$ctrl.vals"
        ng-options="item.value as item.key for item in $ctrl.mapped"
        ng-change="$ctrl.onChange()" name="{{$ctrl.name}}"
        size="{{$ctrl.data.length}}" multiple>
</select>

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