EmberJS My latest project has me working on EmberJS.

Because at this point, what’s one more JavaScript client framework? In all seriousness, though, this has the benefit that I get to see lots of different technologies. It also has the downside that I do not get to work with a single technology long enough to get really good at it.

Our current problem is something along this line. We have a nested array of strings to hold the street address. We kicked around a few different solutions, but ended up with the most dynamic possible answer. It was also the trickiest solution, but that tends to be expected.

Here’s a quick-and-dirty version of the model.

App.ShippingAddress = DS.Model.extend({
  name: DS.attr('string'),
  address: DS.attr({
    defaultValue: function () {
      return [];
    }
  })
});

Instead of having separate fields for the different address parts, it is stored as a single array of strings in the database.

This problem here is that an array of strings is not bindable in Ember. Ember would much rather work with objects. To fix this, we added a computed property to the ShippingAddress. This function converts each line string into an simple {value: <line>} object.

App.ShippingAddress = DS.Model.extend({
  name: DS.attr('string'),
  address: DS.attr({
    defaultValue: function () {
      return [];
    }
  }),

  editableAddress: Ember.computed('address', function () {
    var address = this.get('address');
    return address.map(function (line) {
      return { value: line };
    });
  })
});

In our template, we now work with model.editableAddress, instead of the original address property.

<ul>
  {{#each model.editableAddress as |line index|}}
    <li>
      {{input value=line.value}}
      <span {{action 'removeLine' index}} style="cursor: pointer;">[-]</span>
    </li>
  {{/each}}
  <li>
    <span {{action 'addLine'}} style="cursor: pointer;">[+]</span>
  </li>
</ul>

When addLine and removeLine are used, their code will look like this. Note that we are adding a new object to the editableAddress.

addLine() {
  var editableAddress = this.get('model.editableAddress');
  editableAddress.pushObject({ value: '' });
},
removeLine(index) {
  var editableAddress = this.get('model.editableAddress');
  editableAddress.removeAt(index);
},

The only step remaining is to set the new value of address based on what is currently stored in editableAddress.

function updateShippingAddress() {
  var editableAddress = this.get('model.editableAddress');
  var address = [];
  editableAddress.forEach(function (line) {
    if (line.value && line.value.trim().length) {
      address.push(line.value.trim());
    }
  });
  this.get('model').set('address', address);
}

Check out the working demo.

Notes

Special thanks to John Daley and Chad Moore for their insights on this bug.