excellent. and good description too.
Thank you so much dan!!
On Mar 24, 5:14 pm, "Dan Dorman" <[EMAIL PROTECTED]> wrote:
> On Mon, Mar 24, 2008 at 5:49 PM, dave <[EMAIL PROTECTED]> wrote:
> > The mousedown event is created as well. Now Click in the blue box...
> > the event is received, but the class doesn't know the value of it's
> > member anymore...
>
> It's basically a context issue.
>
> From your code:
>
> this.div.observe('mousedown', this.mouseDown);
>
> Which is great: it sets up the mouseDown function of your class to
> respond to the onmousedown event. However, when that div calls the
> observe() method, Prototype automatically sets up the event handler so
> that it is /div/ that gets treated as "this" when the event is
> triggered.
>
> It's sort of like div has its own copy of your class's mouseDown
> method, so when mouseDown() actually starts running, and it gets to
> the line
>
> $('output').innerHTML += (this.div + "<br>");
>
> the "this.div" is being parsed as "div.div"--and div doesn't /have/ a
> div property. Hence the undefined.
>
> Fortunately, it's easy to put that function back into the proper
> context, by "binding" the scope of the event handling function.
> Revisiting that first line from your code:
>
> this.div.observe('mousedown', this.mouseDown.bindAsEventListener(this));
>
> Note that call to bindAsEventListener(). The argument is the object
> whose context you want that method to be in when it's actually called.
> So now when mouseDown gets called, your class instance is running the
> show and since it /does/ have a div property, you shouldn't get that
> pesky "undefined."
>
> I'm not sure my explanation was particularly good, but you can find
> out lots more about this from the API
> docs:http://prototypejs.org/api/function(take a look at "bind" /and/
> "bindAsEventListener").
>
> Hope that helps.
>
> :Dan
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "Ruby
on Rails: Spinoffs" group.
To post to this group, send email to rubyonrails-spinoffs@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/rubyonrails-spinoffs?hl=en
-~----------~----~----~----~------~----~------~--~---
