Why do I receive undefined value after reloading page in Meteor?

Question

So I have the following form:

template(name='editUser')
  .row
    .col-md-4.col-md-offset-4
      .page-header
        h1 Edit user
      form#edit-user-form
        .form-group
          label(for='name') Name
          input#user-name.form-control(type='text' placeholder='Name' value='{{user.name}}')
        .form-group
          label(for='email') E-Mail
          input#user-email.form-control(type='text' placeholder='E-Mail' value='{{getEmail user}}')
    button.btn.btn-primary(type='submit') Update

the following handlebars.js-Helper:

Handlebars.registerHelper('getEmail', function (user) {
  if (user.emails && user.emails[0] && user.emails[0].address)
    return user.emails[0].address;
  return '';
  });

and the following iron-Router code:

    EditUserController = RouteController.extend({
      template: 'editUser',
      waitOn: function () {
        return Meteor.subscribe('user', this.params._id);
      },
      data: function () {
        return {
          user: Meteor.users.findOne( { _id: this.params._id } )
        };
      }
});

If I run my application and click on the link to the edit-User-Form I can see the E-Mail Address. But if I change my code and Meteor automatically refreshes the page, the E-Mail-Field is empty and the console says, that it can't fetch the value of undefined.

If I use the same form, but with a with-Helper, the E-Mail is displayed even if Meteor automatically refreshes the page:

template(name='editUser')
  .row
    .col-md-4.col-md-offset-4
      .page-header
        h1 Edit user
      form#edit-user-form
        with user
          .form-group
            label(for='name') Name
            input#user-name.form-control(type='text' placeholder='Name' value='{{name}}')
          .form-group
            label(for='email') E-Mail
            input#user-email.form-control(type='text' placeholder='E-Mail' value='{{getEmail this}}')
      button.btn.btn-primary(type='submit') Update

Why is this so? And should I always use the with-Helper if I get single Results (only one Result to display)?

Thanks in advance!

Answer 1

Replace Meteor.users.findOne with Meteor.users.find.

When findOne doesn’t find anything, it returns undefined which causes your error; when find doesn’t find anything, it returns an empty cursor which Meteor knows what to do with. Essentially all you were doing by adding with was to cause Meteor to check if the value was undefined, but that check isn’t necessary for a cursor, empty or otherwise.