Visualforce: Can't call sort method on List of Comparable objects

Question

I have a list of custom objects whose class "implements Comparable".

In my visualforce page I have {!thelist.sort} as an action for a command link.

I get an error:

action="#{thelist.sort}": Unknown method 'List.sort()'

Sort does work on this object, and if I code a method for the controller like this:

public void sortthelist() {
    thelist.sort();
}

And then call put that in the action then it works.

But this is duff code. I don't want to write a method for every instance of a sortable object. The methods of the object should be exposed in the template itself. This is already the case; I can call List.size() in a visualforce page.

Is there something I'm missing or is this a bug/feature?

Answer 1

This is a limitation of the Visualforce engine; lists and sets get cast into something like VisualforceArray, and maps into some other class. While I don't specifically recall their names, it's important to know that they are a superset of the Apex Code collections that have limited functionality. For example, you can't call isEmpty on a VisualforceArray, you have to instead compare size to 0. These odd discrepancies abound in Visualforce. Maps, as another example, will throw fatal exceptions if you reference a key that doesn't exist instead of returning null.