How do I get a null response from a $resource?

Question

I am running this:

angular.module("services").factory('Member', function($resource) {
  var Member = $resource('/api/v1/member.json');

  Member.current = Member.get();

  return Member;
});

But the server is responding with:

null

Because the user is not logged in.

But when I log the result I get this:

Resource
  0: "n"
  1: "u"
  2: "l"
  3: "l"
  $promise: Object
  $resolved: true
  __proto__: Resource

Where as I would have expected literally null.

why do these good unasked questions get so little attention these days? Btw @stewie answered the question on the point (y) — angabriel, Jan 23 '14 at 22:45

Stewie · Accepted Answer · 2014-01-22T22:51:48.550

$resource.get method, by default, expects the JSON response to be an object (when parsed). When calling $resource.get(), the result is going to be an instance of the $resource.

In your example, calling Member.get({id:1}) will produce a $resource instance that is created by calling new Member() ^source and then populated ^source (when XHR is completed) with properties of the parsed JSON response:

shallowClearAndCopy(data, value);

The signature of the function with which your Member instance is populated is as follows:

function shallowClearAndCopy(src, dst) {
  dst = dst || {};

  angular.forEach(dst, function(value, key){
    delete dst[key];
  });

  for (var key in src) {
    if (src.hasOwnProperty(key) && key.charAt(0) !== '$' && key.charAt(1) !== '$') {
      dst[key] = src[key];
    }
  }

  return dst;
}

Glancing the function body you will realise that the function does not expect src parameter to be anything else but object (for (var key in src) { ...). So, if you provide it with string "null" the result will be:

{1: "n", 2: "u", 3: "l", ...}

ngResource is built to support a RESTfull API with JSON as an implied data transfer format, hence you won't be able to use responses such as "null" or anything else which isn't a valid JSON.

Unless.

Unless you make use of transformResponse to convert "null" to something like {'null': true} on the fly:

app.factory('Member', function($resource) {
  var Member = $resource('member.txt', {}, {
    get: {
      method: 'GET',
      isArray: false,
      transformResponse: function(data, headersGetter){
        if(data === 'null'){
          return {null: true};
        }
        return angular.fromJson(data);
      }
    }
  });
  return Member;
});

$scope.member = Member.get({id: 1});
console.log($scope.member); // --> {null: true}

DEMO

score 2 · Answer 2 · edited Dec 03 '22 at 22:10

Your code looks fine. But seeing this kind of output in the console is a pain in the -muted-. One wants to fix it right away, setting any options for result formats, changing urls, http/https // fiddling etc.

But the thing is

Calling a URL which is not allowed, because the user is not logged in.

One expects a nice 403 so $resources fault handler executes.

This way your result handler does not execute at all ;)

Member.current = Member.get; //note removed () here

// then outside call:
Member.current(
  function(result) {
    // should not execute for 403
  }, 
  function(fault) {
    // TODO: handle case: 'user not logged in'
  });

How do I get a null response from a $resource?

2 Answers2