Error: error:trkslct

Comprehension expression cannot contain both `select as` and `track by` expressions.

NOTE: This error was introduced in 1.3.0-rc.5, and was removed for 1.3.0-rc.6 in order to not break existing apps.

This error occurs when 'ngOptions' is passed a comprehension expression that contains both a select as expression and a track by expression. These two expressions are fundamentally incompatible.

• Example of bad expression: <select ng-options="item.subItem as item.label for item in values track by item.id" ng-model="selected"> values: [{id: 1, label: 'aLabel', subItem: {name: 'aSubItem'}}, {id: 2, label: 'bLabel', subItem: {name: 'bSubItem'}}], $scope.selected = {name: 'aSubItem'};
• track by is always applied to value, with purpose to preserve the selection, (to item in this case)
• To calculate whether an item is selected, ngOptions does the following:
  1. apply track by to the values in the array: In the example: [1,2]
  2. apply track by to the already selected value in ngModel: In the example: this is not possible, as track by refers to item.id, but the selected value from ngModel is {name: aSubItem}.

Here's an example of how to make this example work by using track by without select as:

<select ng-model="selected" ng-options="item.label for item in values track by item.id">

Note: This would store the whole item as the model to scope.selected instead of item.subItem.

For more information on valid expression syntax, see 'ngOptions' in select directive docs.