Access scope variables from a filter in AngularJS

问题:

I am passing date value to my custom filter this way:

angular.module('myapp').
  filter('filterReceiptsForDate', function () {
    return function (input, date) {
      var out = _.filter(input, function (item) {
        return moment(item.value.created).format('YYYY-MM-DD') == date;
      });
      return out;
    }
  });

I would like to inject a couple of scope variables there too, like what I can do in directives. Is that possible to do this without having to passing these vars explicitly as function arguments?

回答1:

Apparently you can.

Usually you would pass scope variables to the filter as function parameter:

function MyCtrl($scope){
  $scope.currentDate = new Date();
  $scope.dateFormat = 'short';
}

<span ng-controller="MyCtrl">{{currentDate | date:dateFormat}}</span> // --> 7/11/13 4:57 PM

But, to pass the current scope in, you'd have to pass this:

<span ng-controller="MyCtrl">{{currentDate | date:this}}</span>

and this will be a reference to current scope:

Simplified:

app.controller('AppController',
    function($scope) {
      $scope.var1 = 'This is some text.';
      $scope.var2 = 'And this is appended with custom filter.';
    }
  );


app.filter('filterReceiptsForDate', function () {
  return function (input, scope) {
    return input + ' <strong>' + scope.var2 + '</strong>';
  };
});

<div ng-bind-html-unsafe="var1 | filterReceiptsForDate:this"></div>
<!-- Results in: "This is some text. <strong>And this is appended with custom filter.</strong>" -->

PLUNKER

Warning:

1. Be careful with this and use scope only to read the values inside the filter, because otherwise you will easily find your self in $digest loop.
2. Filters that require such a "heavy" dependency (the whole scope) tend to be very difficult to test.

回答2:

I found that this references local $scope. Not sure if this is safe way of accessing it.