[Potlatch-dev] Introducing Magic Roundabout tool

[Dave Stubbs]

On Sat, Feb 26, 2011 at 2:23 AM, Steve Bennett <stevagewp at gmail.com> wrote:
> On Sat, Feb 26, 2011 at 2:52 AM, Dave Stubbs <osm.list at randomjunk.co.uk> wrote:
>> Yeah, what we have is a nested and OO implementation of a simple stack
>> with markers. This allows you to do cool stuff like encapsulate
>> complex actions without bothering the user with extra undo steps or
>> adding lots of boiler plate code around the "RecordAction" stage.
>
> Don't get me wrong, I think the implementation is fantastic. The only
> thing I'm commenting on is some of the unintuitive naming and
> mechanics.
>
> For example, passing a function to an operation, where the function
> represents a storage operation for an undoable action...is not very
> intuitive. In practice, exactly one of two things gets passed to those
> functions: either MainUndoStack.getInstance().push, or some
> CompositeUndoableAction.addAction. It would therefore be possible to
> replace declarations like this:
>
> public function createWay(tags:Object, nodes:Array,
> performCreate:Function):Way {
>            var way:Way = new Way(nextNegative, 0, tags, true, nodes.concat());
>            performCreate(new CreateEntityAction(way, setWay));
> ...
>
> with
>
> public function createWay(tags:Object, nodes:Array, actionStack:
> CompositeUndoableAction=null):Way {
>            var way:Way = new Way(nextNegative, 0, tags, true, nodes.concat());
>            recordAction(actionStack, new CreateEntityAction(way, setWay));
> ...
>
> where recordAction is:
>
> protected function recordAction(stack: CompositeUndoAbleAction,
> action: Action):void {
>  if (stack)
>    stack.push(action)
>  else
>    MainUndoStack.getInstance().push(action);
> }
>
> Personally, I think passing either a composite action stack, or null,
> to an operation is a lot more intuitive than passing a function. And
> it would make some simpler:
>
> w = createWay({}, nodes);
>
> Now, the fact that it's creating an action which is being placed on
> the main undo stack is totally invisible. Magic behind the scenes, and
> all that.
>

Whether passing functions or objects is more intuitive kind of depends
where you're coming from :-)

The main difference is the null passing -- and you can do that with
the function.
Personally I prefer the explicit decision of the caller as to where to
put it, but there's not a lot in it.

Dave