Is this a “Deferred Antipattern”?

Question

I\'m finding it hard to understand the \"deferred antipattern\". I think I understand it in principal but I haven\'t seen a super simple example of what a service, with a di

Answer 1

Using the $q constructor is a deferred anti-pattern

ANTI-PATTERN

vm.download = function() {
  var url = "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf";    
  return $q(function(resolve, reject) {    
    var req = {
      method: 'POST',
      url: url,
      responseType: 'arraybuffer'
    };   
    $http(req).then(function(response) {
      resolve(response.data);
    }, function(error) {
      reject(error);
    });
  });
}

CORRECT

vm.download = function() {
    var url = "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf";    
    var req = {
      method: 'POST',
      url: url,
      responseType: 'arraybuffer'
    };   
    return $http(req).then(function(response) {
        return response.data;
    });
}

The $http service already returns a promise. Using the $q constructor is unnecessary and error prone.