order-detail.js

    model.eachAttribute(function(name, meta) {
      var methodName = name + "Valid";
      var errorsKey = "errors." + name;

      var method = function() {
        var isValid = Ember.isEmpty(this.get(errorsKey));
        if (isValid) {
          return 'valid';
        } else {
          return 'input--error';
        }
      }.property(errorsKey)

      _this.set(methodName, method);
    });