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Walter Lee Davis

2008-Jan-18 15:33 UTC

design pattern help needed for periodical updater

I am trying to make a gallery of photos poll the server and see if  
there''s anything more recent. I am having trouble figuring out how to  
get Ajax.PeriodicalUpdater to send a dynamic value to the server. Is  
this something I can set up in onCreate? If so, how do I then add it  
to the parameters before the post is sent?

This, very obviously, doesn''t work -- it keeps sending the same value  
for "last", even though my updater script destroys and replaces the  
span $(''latest'') if it notices a change:

Event.observe(window,''load'',function(){
	new
Ajax.PeriodicalUpdater(''gallery'',''update.php'',{
		parameters: {last:$(''latest'').innerHTML},
		insertion: Insertion.Top,
		frequency:30,
		decay:2
		}
	);
});

Thanks in advance,

Walter

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Justin Perkins

2008-Jan-18 15:43 UTC

head link

Re: design pattern help needed for periodical updater

On Jan 18, 2008 9:33 AM, Walter Lee Davis
<waltd-HQgmohHLjDZWk0Htik3J/w@public.gmane.org>
wrote:>
> I am trying to make a gallery of photos poll the server and see if
> there''s anything more recent. I am having trouble figuring out how
to
> get Ajax.PeriodicalUpdater to send a dynamic value to the server.
Parameters are just normal key/value pairs, same as form POSTs and
querystrings. You can build up the parameters separately pass them to
the parameters option as either an ampersand (&) separated list of
key/values, or you can pass in a Hash object. Note the lack of curly
brackets (hash object) if using the string method vs. the second style
which uses a hash.

new
Ajax.PeriodicalUpdater(''gallery'',''update.php'',{
               parameters: ''latest='' +
escape($(''latest'').innerHTML),
               insertion: Insertion.Top,
               frequency:30,
               decay:2
               }
       );

// or...
new
Ajax.PeriodicalUpdater(''gallery'',''update.php'',{
               parameters: { latest: $(''latest'').innerHTML },
               insertion: Insertion.Top,
               frequency:30,
               decay:2
               }
       );




-justin

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Richard Quadling

2008-Jan-18 15:56 UTC

head link

Re: design pattern help needed for periodical updater

On 18/01/2008, Justin Perkins
<justinperkins-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> On Jan 18, 2008 9:33 AM, Walter Lee Davis
<waltd-HQgmohHLjDZWk0Htik3J/w@public.gmane.org> wrote:
> >
> > I am trying to make a gallery of photos poll the server and see if
> > there''s anything more recent. I am having trouble figuring
out how to
> > get Ajax.PeriodicalUpdater to send a dynamic value to the server.
>
> Parameters are just normal key/value pairs, same as form POSTs and
> querystrings. You can build up the parameters separately pass them to
> the parameters option as either an ampersand (&) separated list of
> key/values, or you can pass in a Hash object. Note the lack of curly
> brackets (hash object) if using the string method vs. the second style
> which uses a hash.
>
> new
Ajax.PeriodicalUpdater(''gallery'',''update.php'',{
>                parameters: ''latest='' +
escape($(''latest'').innerHTML),
>                insertion: Insertion.Top,
>                frequency:30,
>                decay:2
>                }
>        );
>
> // or...
> new
Ajax.PeriodicalUpdater(''gallery'',''update.php'',{
>                parameters: { latest:
$(''latest'').innerHTML },
>                insertion: Insertion.Top,
>                frequency:30,
>                decay:2
>                }
>        );
>
>
>
>
> -justin
>
Justin, I think you missed the bit about this being a periodical
updater. The same data is sent each time.

Walter, I use the following code to timestamp all my AJAX calls. Makes
sure each one is a unique request. Maybe you can adapt it.

Ajax.Responders.register
	({
	onCreate: function(o_Requester)
		{
		// Timestamp each AJAX action.
		var o_Date = new Date();
		o_Requester.url 			o_Requester.url +
			(o_Requester.url.indexOf(''?'') == -1 ? ''?''
: ''&'') +
			''Stamp='' + o_Date.getTime();
		if (b_Debug) { console.groupEnd(); }
		},
	});


-- 
-----
Richard Quadling
Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498&r=213474731
"Standing on the shoulders of some very clever giants!"

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Walter Lee Davis

2008-Jan-18 15:59 UTC

head link

Re: design pattern help needed for periodical updater

On Jan 18, 2008, at 10:43 AM, Justin Perkins wrote:
>                parameters: { latest:
$(''latest'').innerHTML },

Thanks, but this is precisely what I am doing in my example, and it  
isn''t working -- each time the PeriodicalUpdater fires, it sends the  
same value, even though it does update the page with newer photos.  
Trouble is, it keeps sending the same updated photos over and over,  
never getting the message that "latest" is different.

Is there a scope issue here? Is the fact that the updater is wrapped  
inside a page listener the reason why the variable value never changes?

Thanks again,

Walter

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Justin Perkins

2008-Jan-18 16:06 UTC

head link

Re: design pattern help needed for periodical updater

On Jan 18, 2008 9:59 AM, Walter Lee Davis
<waltd-HQgmohHLjDZWk0Htik3J/w@public.gmane.org>
wrote:> Thanks, but this is precisely what I am doing in my example, and it
> isn''t working -- each time the PeriodicalUpdater fires,
Sorry Walter, misread your code as just sending the raw data, not as a
key/value pair.

Have you considered keeping track of the latest photo ID with a
javascript variable, which would be updated with every Ajax request?

What does your HTML look like and what is a typical response from the server?

Personally, I would turn evalScripts on, leave the first parameter of
the Ajax.PeriodicalUpdater as an empty string (so nothing on the page
is updated), then return plain JavaScript from the server (to insert
new photos and update a variable used to keep track of the latest
photo ID).

-justin

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Ken Snyder

2008-Jan-18 16:08 UTC

head link

Re: design pattern help needed for periodical updater

Walter Lee Davis wrote:> I am trying to make a gallery of photos poll the server and see if  
> there''s anything more recent. I am having trouble figuring out how
to
> get Ajax.PeriodicalUpdater to send a dynamic value to the server. Is  
> this something I can set up in onCreate? If so, how do I then add it  
> to the parameters before the post is sent?
>
> This, very obviously, doesn''t work -- it keeps sending the same
value
> for "last", even though my updater script destroys and replaces
the
> span $(''latest'') if it notices a change:
>
> Event.observe(window,''load'',function(){
> 	new
Ajax.PeriodicalUpdater(''gallery'',''update.php'',{
> 		parameters: {last:$(''latest'').innerHTML},
> 		insertion: Insertion.Top,
> 		frequency:30,
> 		decay:2
> 		}
> 	);
> });
>   
Try PeriodicalExecuter and Ajax.Updater:

var updateGalery = function() {
  new Ajax.Updater(''gallery'', ''update.php'',
{
    parameters: {last: $(''latest'').innerHTML},
    insertion: Insertion.Top
  });
};

document.observe(''dom:loaded'', function() {
  new PeriodicalExecuter(updateGalery, 30);
});


- Ken Snyder

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Matt Foster

2008-Jan-18 16:08 UTC

head link

Re: design pattern help needed for periodical updater

That would make sense that the value is constant.  You''re sending a
string value, not an object reference.

I understand what you''re trying to do but it is simply not going to
work, the string value is "copied by value" and whether or not the
property changes it isn''t going to affect the value sent to the
constructor.

You need some way to have the PE retrieve fresh parameters and that
may not be possible in this implementation.  On the other end of
things, you could potentially use session data to maneuver it so the
back end knows what is the latest image and send it that way.
Alternatively it isn''t hard to roll your own PE with a Ajax.Request
and setInterval.

Good Luck,
              Matt

On Jan 18, 10:59 am, Walter Lee Davis
<wa...-HQgmohHLjDZWk0Htik3J/w@public.gmane.org>
wrote:> On Jan 18, 2008, at 10:43 AM, Justin Perkins wrote:
>
> >                parameters: { latest:
$(''latest'').innerHTML },
>
> Thanks, but this is precisely what I am doing in my example, and it
> isn''t working -- each time the PeriodicalUpdater fires, it sends
the
> same value, even though it does update the page with newer photos.
> Trouble is, it keeps sending the same updated photos over and over,
> never getting the message that "latest" is different.
>
> Is there a scope issue here? Is the fact that the updater is wrapped
> inside a page listener the reason why the variable value never changes?
>
> Thanks again,
>
> Walter--~--~---------~--~----~------------~-------~--~----~
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Walter Lee Davis

2008-Jan-18 16:53 UTC

head link

Re: design pattern help needed for periodical updater

On Jan 18, 2008, at 10:56 AM, Richard Quadling wrote:
> Justin, I think you missed the bit about this being a periodical
> updater. The same data is sent each time.
>
> Walter, I use the following code to timestamp all my AJAX calls. Makes
> sure each one is a unique request. Maybe you can adapt it.
>
> Ajax.Responders.register
> 	({
> 	onCreate: function(o_Requester)
> 		{
> 		// Timestamp each AJAX action.
> 		var o_Date = new Date();
> 		o_Requester.url > 			o_Requester.url +
> 			(o_Requester.url.indexOf(''?'') == -1 ?
''?'' : ''&'') +
> 			''Stamp='' + o_Date.getTime();
> 		if (b_Debug) { console.groupEnd(); }
> 		},
> 	});
>
>
> --  
> -----
> Richard Quadling
> Zend Certified Engineer :
http://zend.com/zce.php?c=ZEND002498&r=213474731
> "Standing on the shoulders of some very clever giants!"
Thanks very much to you and the clever giants! The following worked  
perfectly:

Ajax.Responders.register({
	onCreate: function(o_Requester){
		// Get fresh variables
		var latest = $(''latest'').innerHTML;
		o_Requester.url 			o_Requester.url +
			(o_Requester.url.indexOf(''?'') == -1 ? ''?''
: ''&'') +
			''last='' + latest;
		if (b_Debug) { console.groupEnd(); }
	}
});

This keeps the value of ''latest'' in line with reality over the
lifetime of the updater.

Thanks again!

Walter



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Richard Quadling

2008-Jan-19 11:01 UTC

head link

Re: design pattern help needed for periodical updater

If you have multiple AJAX requests (not repeated ones, but different
ones), then they will ALL get the latest value, so watch out for that.



On 18/01/2008, Walter Lee Davis
<waltd-HQgmohHLjDZWk0Htik3J/w@public.gmane.org>
wrote:>
>
> On Jan 18, 2008, at 10:56 AM, Richard Quadling wrote:
>
> > Justin, I think you missed the bit about this being a periodical
> > updater. The same data is sent each time.
> >
> > Walter, I use the following code to timestamp all my AJAX calls. Makes
> > sure each one is a unique request. Maybe you can adapt it.
> >
> > Ajax.Responders.register
> >       ({
> >       onCreate: function(o_Requester)
> >               {
> >               // Timestamp each AJAX action.
> >               var o_Date = new Date();
> >               o_Requester.url > >                      
o_Requester.url +
> >                       (o_Requester.url.indexOf(''?'')
== -1 ? ''?'' : ''&'') +
> >                       ''Stamp='' + o_Date.getTime();
> >               if (b_Debug) { console.groupEnd(); }
> >               },
> >       });
> >
> >
> > --
> > -----
> > Richard Quadling
> > Zend Certified Engineer :
http://zend.com/zce.php?c=ZEND002498&r=213474731
> > "Standing on the shoulders of some very clever giants!"
>
> Thanks very much to you and the clever giants! The following worked
> perfectly:
>
> Ajax.Responders.register({
>         onCreate: function(o_Requester){
>                 // Get fresh variables
>                 var latest = $(''latest'').innerHTML;
>                 o_Requester.url >                        
o_Requester.url +
>                         (o_Requester.url.indexOf(''?'') ==
-1 ? ''?'' : ''&'') +
>                         ''last='' + latest;
>                 if (b_Debug) { console.groupEnd(); }
>         }
> });
>
> This keeps the value of ''latest'' in line with reality
over the
> lifetime of the updater.
>
> Thanks again!
>
> Walter
>
>
>
> >
>

-- 
-----
Richard Quadling
Zend Certified Engineer : http://zend.com/zce.php?c=ZEND002498&r=213474731
"Standing on the shoulders of some very clever giants!"

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Walter Lee Davis

2008-Jan-19 17:07 UTC

head link

Re: design pattern help needed for periodical updater

Thanks, I did think about that. In this particular case it''s not an  
issue. If I was going to do this over, I would manually add the  
onCreate bit to the affected instance of the PeriodicalUpdater,  
rather than setting it as a global override for the entire page.

I''m sure there''s a clever way to have my cake and eat it too,
but
this is several levels of abstraction beyond what my feeble  
procedural brain can conceive of!

@Ken -- I thought about your solution, but in the end decided to use  
Richard''s, because the groovy "decay" feature in
PeriodicalUpdater
would be useful for this particular application. Better to override  
the one thing that was vexing me than re-create everything from scratch.

Thanks to everyone!

Walter

PS: here''s the final:

http://philadelphiacathedral.org/mandala/gallery.php

warning: enormous page, crashes MobileSafari, I really need to also  
enable an endless scroll of some sort


On Jan 19, 2008, at 6:01 AM, Richard Quadling wrote:
>
> If you have multiple AJAX requests (not repeated ones, but different
> ones), then they will ALL get the latest value, so watch out for that.
>
>
>
> On 18/01/2008, Walter Lee Davis
<waltd-HQgmohHLjDZWk0Htik3J/w@public.gmane.org> wrote:
>>
>>
>> On Jan 18, 2008, at 10:56 AM, Richard Quadling wrote:
>>
>>> Justin, I think you missed the bit about this being a periodical
>>> updater. The same data is sent each time.
>>>
>>> Walter, I use the following code to timestamp all my AJAX calls.  
>>> Makes
>>> sure each one is a unique request. Maybe you can adapt it.
>>>
>>> Ajax.Responders.register
>>>       ({
>>>       onCreate: function(o_Requester)
>>>               {
>>>               // Timestamp each AJAX action.
>>>               var o_Date = new Date();
>>>               o_Requester.url >>>                      
o_Requester.url +
>>>                      
(o_Requester.url.indexOf(''?'') == -1 ? ''?'' :
>>> ''&'') +
>>>                       ''Stamp='' +
o_Date.getTime();
>>>               if (b_Debug) { console.groupEnd(); }
>>>               },
>>>       });
>>>
>>>
>>> --
>>> -----
>>> Richard Quadling
>>> Zend Certified Engineer : http://zend.com/zce.php? 
>>> c=ZEND002498&r=213474731
>>> "Standing on the shoulders of some very clever giants!"
>>
>> Thanks very much to you and the clever giants! The following worked
>> perfectly:
>>
>> Ajax.Responders.register({
>>         onCreate: function(o_Requester){
>>                 // Get fresh variables
>>                 var latest = $(''latest'').innerHTML;
>>                 o_Requester.url >>                        
o_Requester.url +
>>                         (o_Requester.url.indexOf(''?'')
== -1 ?
>> ''?'' : ''&'') +
>>                         ''last='' + latest;
>>                 if (b_Debug) { console.groupEnd(); }
>>         }
>> });
>>
>> This keeps the value of ''latest'' in line with reality
over the
>> lifetime of the updater.
>>
>> Thanks again!
>>
>> Walter
>>
>>
>>
>>>
>>
>
>
> -- 
> -----
> Richard Quadling
> Zend Certified Engineer : http://zend.com/zce.php? 
> c=ZEND002498&r=213474731
> "Standing on the shoulders of some very clever giants!"
>
> >

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Walter Lee Davis

2008-Jan-19 17:12 UTC

head link

Re: design pattern help needed for periodical updater

Errrr. No sooner do I post this than something goes haywire with the  
remote camera and it uploads a bunch of really old photos from the  
original testing, and messes up the modification dates of same.

I am really getting tired of driving down to the Cathedral!

Walter

On Jan 19, 2008, at 12:07 PM, Walter Lee Davis wrote:
> PS: here''s the final:
>
> http://philadelphiacathedral.org/mandala/gallery.php
>
> warning: enormous page, crashes MobileSafari, I really need to also
> enable an endless scroll of some sort

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Rails spinoffs - Jan 2008 - design pattern help needed for periodical updater

design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater

Re: design pattern help needed for periodical updater