I don't like the way it is now. That sounds more like a validator workflow.
Having DateFormatter require IDateChooserModel doesn't sound right. I think
the goal of the current implementation was to not require the views to know
about the formatter. Then you could change what the view would display by
using a different formatting bead. Maybe that was a bad idea. I think you are
proposing that the views know they are using a formatter.
Let's think about how we want Formatters to be used. The first question that
comes to mind is whether the common case is that a single formatting
"algorithm" would be used throughout an application. If so, then scattering
formatting beads on strands in different places in the application will be
painful to manage unless you have a central config to manage them.
IOW, I think it would be rare for dates or currency to be formatted in one way
in some component and differently in some other component.
The second thing to consider is loose-coupling. How will the View find a
formatter? The advantage of beads is that formatters can be replaced, but only
if the view finds the formatter by interface name. But then they might be able
to find the formatter some other way anyway. Related: should the presence of a
formatter be optional? I think not in the common case. The view shouldn't
have to worry about the formatter not being there when expected. A view either
needs a formatter or it doesn’t.
Next question: How should views be able to use formatters when written in
MXML? If there is a shared formatter, that implies function call binding which
is sort of heavy. Having a bead for each property being formatted allows the
binding system to use SimpleBinding which is cheaper/faster. But I think it
might be too painful to have a formatter instance for each formatted property.
So, maybe it is better to have Views expect formatters. But maybe formatters
should be Singletons so they are shared.
Thoughts?
-Alex
On 1/17/19, 9:36 AM, "Andrew Wetmore" <cottag...@gmail.com> wrote:
This simplification sounds good. Will you be annotating how to use the new
bead structures, maybe with some examples, for those of us who are lost
among the strands?
On Thu, Jan 17, 2019 at 12:26 PM Harbs <harbs.li...@gmail.com> wrote:
> I have the occasion this week to deal with the formatter classes, and I’d
> like to make some changes. I’d like input from others on the subject.
>
> Taking SimpleDateFormatter as an example:
> 1. The Formatter assumes that its being attached to a Strand with an
> IDateChooserModel.
> 2. It requires a “propertyName to be set and concatenates that with
> “Changed” and adds an event listener to the model.
> 3. When the property is changed, it formats the result which must be a
> “selectedDate” and then dispatches an event.
> 4. The view bead must attach an event listener to the Formatter to get
> notification when the format changes.
> 5. It also invariably attaches an event listener to the model when the
> model changes.
> 6. When the model changes we have first an event picked up by the
> formatter and then the formatter dispatches a separate event which is
> picked up by the view. The view then explicitly gets the formatted date
> from the formatter.
>
> That’s a lot of indirection for no apparent reason. It also limits how a
> formatter can be used. A DateFormatter can only be used in conjunction
with
> a IDateChooserModel and it can only format a “selectedDate”. I ran into
> issues when trying to figure out how to use the formatters with date
ranges.
>
> I want to change it to the following:
>
> 1. Make the formatter classes very simple Beads.
> 2. It will make no assumptions on there being any other beads and will not
> attach any event listeners.
> 3. Likewise, it will not dispatch any events.
> 4. Date Formatter classes would have a format(date:Date):String method
> which would take any valid date and return the formatted string.
> 5. When a view needs to update a formatted date, it would simply get the
> format bead and call format(). This would allow the bead to be
instantiated
> by any class and would greatly simplify the code.
>
> I’d make similar changes to the other formatter classes.
>
> Any objections to these changes?
>
> Harbs
--
Andrew Wetmore
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