Setting *.prototype methods inside angular factory not working

Question

I'm creating an angular factory that encapsulates and injectable type that can be new-ed up as such:

(function() {
angular
  .module('app')
  .factory('PaymentStream', [

function() {

    function PaymentStream(){

        this._endingBalance = null;
    }

    PaymentStream.prototype.serialize = function() {

        // method body here
    };

    return PaymentStream;

   }]);
})();

When I create a PaymentStream via new PaymentStream() only the constructor seems to have been called. If I don't use prototype and just define the methods inside the constructor it works but then I'm redefining the functions with each instance.

Any idea why those prototypes are not being set?

Edit

Here is how it is being used in the outside.

    function addStreamFunctions(stream) {

        angular.merge(stream, new PaymentStream());
    }

Answer 1

So basing on your edit, The factory was indeed working correctly. The problem is the way you used it, you angular.merge d the new ed object with another object, so its type is not a PaymentStream anymore, the resulting object became a 'generic' object

If the stream is a plain object, what you can do is pass the stream variable in the constructor of PaymentStream and do the merging manually inside your constructor function. Something like

function PaymentStream(stream){

    this._endingBalance = null;

    var keys = Object.keys(stream); //get all properties from the stream

    keys.forEach(function(key){
       this[key] = stream[key];   //put each one in the instance of your object;
    });

}

then use it like

function addStreamFunctions(stream) {

    var stream = new PaymentStream(stream);

}

this code is untested, please tell me if it worked or not :)

Answer 2

Since you are working with factory you need to return an instance of the object, in this case a new instance of PaymentStream

(function() {
  angular.module('my-app').factory('PaymentStream', [function() {
    function PaymentStream() {
      this._endingBalance = null;
    }

    PaymentStream.prototype.serialize = function() {
      // method body here
    };

    return new PaymentStream();
  }]);
})();