What is the best way to conditionally apply a class?

Question

Lets say you have an array that is rendered in a ul with an li for each element and a property on the controller called selectedIndex.

Answer 1

If you want to go beyond binary evaluation and keep your CSS out of your controller you can implement a simple filter that evaluates the input against a map object:

angular.module('myApp.filters, [])
  .filter('switch', function () { 
      return function (input, map) {
          return map[input] || '';
      }; 
  });

This allows you to write your markup like this:

    ...