How should errors be handled when using the Ember.js Data RESTAdapter?

Question

ember-data.js: https://github.com/emberjs/data/tree/0396411e39df96c8506de3182c81414c1d0eb981

In short, when there is an error, I want to display error messages in the view, and then the user can 1) cancel, which will rollback the transaction 2) correct the input errors and successfully commit the transaction, passing the validations on the server.

Below is a code snippet from the source. It doesn't include an error callback.

updateRecord: function(store, type, record) {
  var id = get(record, 'id');
  var root = this.rootForType(type);

  var data = {};
  data[root] = this.toJSON(record);

  this.ajax(this.buildURL(root, id), "PUT", {
    data: data,
    context: this,
    success: function(json) {
      this.didUpdateRecord(store, type, record, json);
    }
  });
},

Overall, what is the flow of receiving an error from the server and updating the view? It seems that an error callback should put the model in an isError state, and then the view can display the appropriate messages. Also, the transaction should stay dirty. That way, the transaction can use rollback.

It seems that using store.recordWasInvalid is going in the right direction, though.

There is not yet a complete mechanism for handling errors, see github.com/emberjs/data/pull/376, perhaps you will find what you want. — sly7_7
Yes, the lack of error handling is surprising, but it's nice that there's no error handling as opposed to a naive implementation that will change later. I've written my recent Ember app to avoid server errors by performing some validations on the client-side, before doing App.store.commit(). — Mars

Sherwin Yu Sherwin Yu · Accepted Answer · 2012-12-12T17:30:58

This weekend I was trying to figure the same thing out. Going off what Luke said, I took a closer look at the ember-data source for the latest commit (Dec 11).

TLDR; to handle ember-data update/create errors, simply define becameError() and becameInvalid(errors) on your DS.Model instance. The cascade triggered by the RESTadapter's AJAX error callback will eventually call these functions you define.

Example:

App.Post = DS.Model.extend
  title: DS.attr "string"
  body: DS.attr "string"

  becameError: ->
    # handle error case here
    alert 'there was an error!'

  becameInvalid: (errors) ->
    # record was invalid
    alert "Record was invalid because: #{errors}"

Here's the full walk through the source:

In the REST adapter, the AJAX callback error function is given here:

   this.ajax(this.buildURL(root, id), "PUT", {
      data: data,
      context: this,
      success: function(json) {
        Ember.run(this, function(){
          this.didUpdateRecord(store, type, record, json);
        });
      },
      error: function(xhr) {
        this.didError(store, type, record, xhr);
      }
    });

didError is defined here and it in turn calls the store's recordWasInvalid or recordWasError depending on the response:

  didError: function(store, type, record, xhr) {
    if (xhr.status === 422) {
      var data = JSON.parse(xhr.responseText);
      store.recordWasInvalid(record, data['errors']);
    } else {
      store.recordWasError(record);
    }
  },

In turn, store.recordWasInvalid and store.recordWasError (defined here) call the record (a DS.Model)'s handlers. In the invalid case, it passes along error messages from the adapter as an argument.

 recordWasInvalid: function(record, errors) {
    record.adapterDidInvalidate(errors);
  },

  recordWasError: function(record) {
    record.adapterDidError();
  },

DS.Model.adapterDidInvalidate and adapterDidError (defined here) simply send('becameInvalid', errors) or send('becameError') which finally leads us to the handlers here:

  didLoad: Ember.K,
  didUpdate: Ember.K,
  didCreate: Ember.K,
  didDelete: Ember.K,
  becameInvalid: Ember.K,
  becameError: Ember.K,

(Ember.K is just a dummy function for returning this. See here)

So, the conclusion is, you simply need to define functions for becameInvalid and becameError on your model to handle these cases.

Hope this helps someone else; the docs certainly don't reflect this right now.

How should errors be handled when using the Ember.js Data RESTAdapter?

4 Answers