How might I implement conditional grouping in a Select element using angular?

问题

I would like to know if I can include additional logic in angular ng-options attribute for a Select element.

In one case, I have a set of options that are flat and have no groupings associated with them. In another, I have multiple options that may have the same description, however their Id's vary because they are each grouped into categories. Based on the data sent over, I would like to display them as either grouped or not grouped.

GROUPED:

<select ng-model="tcCtrl.SelectedItem" 
        ng-options="item.Id + ' - ' + item.Description 
                    group by item.GroupDescription 
                    for item in ctrl.Context.ItemList }"></select>

NOT GROUPED:

<select ng-model="tcCtrl.SelectedItem" 
        ng-options="item.Id + ' - ' + item.Description 
                    for item in ctrl.Context.ItemList }"></select>

CONDITIONALLY GROUPED ??

If at all possible, I would like to avoid have two separate instances of the select element, however I do no think that the parser for the ngSelectDirective really takes any conditional logic.

Thoughts at good ways to implement something like this?

UPDATE: Here's how the suggested attempt looks...even without any of the 'logic' to build the string.

var optionStr = "item.Id for item in ctrl.Context.Items";
...<select ng-options="{{ ctrl.optionStr }}"></select>...

Problem is when I try binding it the binding doesn't seem to want to stick. If I take the same generated string and replace the {{ property }} then it works fine. I can even confirm in chrome that the string is being rendered in the mark-up.

UPDATE: I have proven that the suggested method does work in a very sterile environment. http://jsfiddle.net/xbws8r5h/

There must be something in my environment that is a variant.

回答1:

Just generate your ng-options expression in JavaScript (controller). Depending of some conditional logic assign different expression.

For example:

<select ng-model="tcCtrl.SelectedItem" 
        ng-options="{{ selectOptions }}"></select>

And your controller might look like:

if(groupCondition){
  $scope.selectOptions = "item.Id + ' - ' + item.Description 
                group by item.GroupDescription 
                for workType in ctrl.Context.ItemList";
} else {
  $scope.selectOptions = "item.Id + ' - ' + item.Description for workType in ctrl.Context.ItemList";
}

Also, shouldn't expression be "... for item in ctrl.Context.ItemList" instead of workType in your case?