When landing on the profile page I get this error

When the Conference app web page is refreshed at the /#/conference link, the endpoints API query fails due to the queryConferences endpoint method not being initialized. After the page is loaded, clicking on a different tab works fine, and then clicking on the "All" tab works.

The error is

TypeError: Cannot read property 'queryConferences' of undefined  at  angular.js:9778

It seems the bootstrapping method for loading the google API does complete in time if the initial page being loaded makes an endpoints API call.

Adding a README file with a link back to the course would be a nice addition.

Problem

1. User navigates to the details page for a conference, in this example conference.maxAttendees is 3 (Registered/Open: 0/3)
2. User registers for the conference (Registered/Open: 1/3)
3. User navigates to another page on the site
4. User navigates back to the details page for the same conference (Registered/Open: 1/3)
5. User unregisters from the conference (Registered/Open: -18/3)

Analysis

The getConference API endpoint returns a ConferenceForm object in which all IntegerField values are actually encoded as strings (wrapped in double quotes), as opposed to integers (no double quotes). This encoding is performed by an internal Google Endpoints method called EndpointsProtoJson.encode_field which is executed during the JSON-encoding process. Due to the integers being encoded as strings in the returned JSON, conference.seatsAvailable (in controller.js) ends up pointing to a string object that represents the number of seats available in the conference, rather than a number object. When the controller.js function unregisterFromConference function gets called, it attempts to add the number 1 to conference.seatsAvailable, but instead the number 1 is converted to a string and concatenated onto the end. In step 5 of the above problem statement, conference.seatsAvailable would point to the string '21' (the concatenation of the string '2' and the number 1). This causes the calculation in conference_detail.html, conference.maxAttendees - conference.seatsAvailable to yield the result -18, instead of the intended 3. The subtraction operator causes both operands to be converted to number objects, then the subtraction is carried out, whereas the addition operator in unregisterFromConference is interpreted as a concatenation operator. If steps 3 and 4 in the above problem statement are skipped, the correct result would be displayed. This is because step 2 causes the controller.js function registerForConference to execute, which subtracts 1 from conference.seatsAvailable thus converting it from a string object to a number object prior to step 5 executing. In this instance, the addition operator does not get interpreted as the concatenation operator because neither of the operands is a string. The addition is then carried out and the correct result displayed.

Solution

A solution to this type of problem is to add a keyword argument called variant with a value of messages.Variant.INT32 to the IntegerField constructor calls in the ConferenceForm class definition in models.py. This prevents the integer values from being wrapped in double quotes in the JSON returned by the API, thus ensuring the values are represented properly in the front-end JavaScript code. As a result, all calculations yield the intended results.

When landing on the app I get this JS error

Landing on the Show conference tab gives me this JS error

In the videos for "Using Transactions", the getConference endpoint appears functional when the instructor uses the site. However, this code is not in any TODO files in lesson 4. Per the forums, this issue was first raised in June.

https://discussions.udacity.com/t/lesson-4-conference-details-not-implemented-how-to-register-to-a-conference/20705