nickponline nickponline - 5 months ago 32
AngularJS Question

How to bind to list of checkbox values with AngularJS?

I have a few checkboxes:

<input type='checkbox' value="apple" checked>
<input type='checkbox' value="orange">
<input type='checkbox' value="pear" checked>
<input type='checkbox' value="naartjie">


That I would like to bind to a list in my controller such that whenever a checkbox is changed the controller maintains a list of all the checked values e.g.
['apple', 'pear']
.

ng-model seems to only be able to bind the value of one single checkbox to a variable in the controller.

Is there another way to do it so that I can bind the four checkboxes to a list in the contrller?

Answer

There are two ways to approach this problem. Either use a simple array or an array of objects. Each solution has it pros and cons. Below you'll find one for each case.


With a simple array as input data

the html could look like:

<label ng-repeat="fruitName in fruits">
  <input
    type="checkbox"
    name="selectedFruits[]"
    value="{{fruitName}}"
    ng-checked="selection.indexOf(fruitName) > -1"
    ng-click="toggleSelection(fruitName)"
  > {{fruitName}}
</label>

and the appropriate controller code would be:

app.controller('SimpleArrayCtrl', ['$scope', function SimpleArrayCtrl($scope) {
  // fruits
  $scope.fruits = ['apple', 'orange', 'pear', 'naartjie'];

  // selected fruits
  $scope.selection = ['apple', 'pear'];

  // toggle selection for a given fruit by name
  $scope.toggleSelection = function toggleSelection(fruitName) {
    var idx = $scope.selection.indexOf(fruitName);

    // is currently selected
    if (idx > -1) {
      $scope.selection.splice(idx, 1);
    }

    // is newly selected
    else {
      $scope.selection.push(fruitName);
    }
  };
}]);

Pros: simple data structure and toggling by name is easy to handle

Cons: add/remove is cumbersome as two lists (the input and selection) have to be managed


With an object array as input data

the html could look like:

<label ng-repeat="fruit in fruits">
  <!--
    - use `value="{{fruit.name}}"` to give the input a real value, in case the form gets submitted
      traditionally

    - use `ng-checked="fruit.selected"` to have the checkbox checked based on some angular expression
      (no two-way-data-binding)

    - use `ng-model="fruit.selected"` to utilize two-way-data-binding. Note that `.selected`
      is arbitrary. The property name could be anything and will be created on the object if not present.
  -->
  <input
    type="checkbox"
    name="selectedFruits[]"
    value="{{fruit.name}}"
    ng-model="fruit.selected"
  > {{fruit.name}}
</label>

and the appropriate controller code would be:

app.controller('ObjectArrayCtrl', ['$scope', 'filterFilter', function ObjectArrayCtrl($scope, filterFilter) {
  // fruits
  $scope.fruits = [
    { name: 'apple',    selected: true },
    { name: 'orange',   selected: false },
    { name: 'pear',     selected: true },
    { name: 'naartjie', selected: false }
  ];

  // selected fruits
  $scope.selection = [];

  // helper method to get selected fruits
  $scope.selectedFruits = function selectedFruits() {
    return filterFilter($scope.fruits, { selected: true });
  };

  // watch fruits for changes
  $scope.$watch('fruits|filter:{selected:true}', function (nv) {
    $scope.selection = nv.map(function (fruit) {
      return fruit.name;
    });
  }, true);
}]);

Pros: add/remove is very easy

Cons: somewhat more complex data structure and toggling by name is cumbersome or requires a helper method


Demo: http://jsbin.com/ImAqUC/1/