Improve the new "as" feature of ngRepeat to include the status of the iteration

[jnizet]

It would be really cool if, in addition to having the possibility to reference the filtered collection using ng-repeat="item in items | filter:x as results (introduced in e0adb9c), the results variable had, inside the ng-repeat, all the attributes set by ng-repeat on the scope ($index, $first, $last, etc.).

This would allow for much cleaner code when nesting ng-repeats. For example:

    <tr ng-repeat="row in rows">
        <td ng-repeat="col in row.columns">
            {{ $parent.$index }}.{{ $index }} - {{ col.value }}
        </td>
    </tr>

could be replaced with the more readable, and safer in case of directives defining their own scopes:

    <tr ng-repeat="row in rows as rowItems">
        <td ng-repeat="col in row.columns as colItems">
            {{ rowItems.$index }}.{{ colItems.$index }} - {{ col.value }}
        </td>
    </tr>

[caitp]

the problem with this is, each scope shares the same reference to the same filtered collection (the alias is actually not in the new child scopes, but in the original scope). This would have to be refactored significantly to work correctly, and it would be costly because we'd be making a copy of the collection for each item.

So, there are ways to curb the cost --- like giving each child scope an object containing a pointer to the collection, as well as the index and stuff, and that might not be so bad --- but I'm not sure about this one.

@matsko what do you think?

[matsko]

Right now the as object is placed on the parent scope not on each of the child scopes. But I really do like the idea here.

@caitp yes that could work. Can't we just update the index directly in the loop for the aliased object? The only issue I can see is if the original collection get's polluted with an $index value. We can't copy the object since that would be a performance hit.

[caitp]

I don't mind it, but it means you'd reference the collection with alias.$collection or something instead of just alias, so that's a bit more inconvenient, in a way

[shahata]

That's a really nice idea. @caitp I can give it a shot this weekend if you don't plan to do it.

[lgalfaso]

you can always create an instance for each loop that has the alias as the prototype and adds the extra properties. This way you can have one instance per loop and do no copies

[petebacondarwin]

How about making the item part of an ng-repeat expression assignable too?? (This doesn't solve the problem of this issue)

<div ng-repeat="myCtrl.item in items">

Or to support this issue you could have yet more syntax (on container):

<div ng-repeat="item on myCtrl in items">

Then the ng-repeat would attach myCtrl.item, myCtrl.$index, myCtrl.$first, etc

[petebacondarwin]

Just to be clear, I think that trying to duplicate the filtered results alias in both the parent and each of the child scopes is a bad idea.

[shahata]

Okay, I think I'm convinced that we need a better syntax for dealing with nested ngRepeat and we should not use the as alias for this. I'll think about it after bed time stories :)

[petebacondarwin]

:-)