How to pass ng-options comprehension_expression to AngularJS component?

Question

I am trying to add a new binding to existing AngularJS component that should take in value of type comprehension_expression as explained in the ng-options Directive API Reference.

Please check the code at the bottom to understand the situation. Note that the top <select> control comes through component named selectField. It does not show any select-options. The bottom control is added directly to index.html and works properly.

I would appreciate if someone can tell me if there is a bug in my script, any alternate approaches to pass value to ng-options attribute to the template, or let me know that there is no way for a component or directive to have such bindings.

angular.module('myApp', [])
  .controller('MainController', function MainController() {
    this.colors = ['red', 'blue', 'green'];
    this.myColor = this.colors[1]; // blue
  }).component('selectField', {
    template: `
      <select ng-model="$ctrl.inputModel"
              ng-options="{{::$ctrl.inputOptionsExpression}}">
      </select>
      Selected: {{$ctrl.inputModel}}</span>
    `,
    bindings: {
      inputModel: '=',
      inputOptionsExpression: '@'
    }
  });

<html>

<head>
  <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.4/angular.min.js"></script>
</head>

<body ng-app="myApp">
  <div ng-controller="MainController as vm">
    <div>
      <select-field input-model="vm.myColor"
                    input-options-expression="color for color in vm.colors">
      </select-field>
    </div>
    <div>
      <select ng-model="vm.myColor" 
              ng-options="color for color in vm.colors">
      </select>
      Selected: {{vm.myColor}}
    </div>
  </div>
</body>

</html>

Possible duplicate of [Why mixing interpolation and expressions is bad practice](https://stackoverflow.com/questions/51592045/why-mixing-interpolation-and-expressions-is-bad-practice). — georgeawg, Aug 09 '18 at 02:14

score 1 · Accepted Answer · answered Aug 09 '18 at 02:57

See Why mixing interpolation and expressions is bad practice.

In this case the ng-options directive will parse the comprehension expression before the interpolation directive renders the desired expression.

Re-write the component to input the choices:

app.component('selectField', {
    require: {ngModelCtrl: 'ngModel'},
    bindings: {
      ngModel: '<',
      choices: '<'
    },
    template: `
      <select ng-model="$ctrl.ngModel"
              ng-change="$ctrl.render($ctrl.ngModel)"
              ̶n̶g̶-̶o̶p̶t̶i̶o̶n̶s̶=̶"̶{̶{̶:̶:̶$̶c̶t̶r̶l̶.̶i̶n̶p̶u̶t̶O̶p̶t̶i̶o̶n̶s̶E̶x̶p̶r̶e̶s̶s̶i̶o̶n̶}̶}̶"̶ ̶
              ng-options="c for c in choices">
      </select>
      Selected: {{$ctrl.ngModel}}</span>
    `,
    controller: function() {
        this.render = (value) => {
            this.ngModelCtrl.$setViewValue(value);
        };
    }
})

Usage:

<select-field ng-model="vm.myColor" choices="vm.colors">
</select-field>

The DEMO

angular.module('myApp', [])
.controller('MainController', function MainController() {
    this.colors = ['red', 'blue', 'green'];
    this.myColor = this.colors[1]; // blue
})
.component('selectField', {
    require: {ngModelCtrl: 'ngModel'},
    bindings: {
      ngModel: '<',
      choices: '<'
    },
    template: `
      <fieldset>Select field
      <select ng-model="$ctrl.ngModel"
              ng-change="$ctrl.render($ctrl.ngModel)"
              ng-options="c for c in $ctrl.choices">
      </select>
      Selected: {{$ctrl.ngModel}}
      </fieldset>
    `,
    controller: function() {
        this.render = (value) => {
            this.ngModelCtrl.$setViewValue(value);
        };
    }
})

<script src="//unpkg.com/angular/angular.js"></script>
<body ng-app="myApp" ng-controller="MainController as vm">
    <div>
      <select-field ng-model="vm.myColor"
                    choices="vm.colors">
      </select-field>
    </div>
    <div>
      <select ng-model="vm.myColor" 
              ng-options="color for color in vm.colors">
      </select>
      Selected: {{vm.myColor}}
    </div>
</body>

How to pass ng-options comprehension_expression to AngularJS component?

1 Answers1

The DEMO