[Seaside] Questions about double (or more) request

[Diogenes Alberto Moreira]

Bueno te lo contesto en castellano y despues trato de traducirlo. en  
otro mail (sorry for english speakers, my English is horrible)

El punto es este, por cada click que haces se ejecuta un continuation  
que esta identificado por el _s para la session _k para el componete  
un numero de &.
en punto que cuando vos le asignas un bloque al call back el bloque se  
lleva el contexto, donde count tiene un valor x, por ejemplo 20

por mas que ejecutes 70 veces, en el contexto del bloque count vale  
20  e incease ejecuta count := 20 + 1.

por eso en el transcript, te aperece increase, incease,  
rendercontentOn y el valor que toma count es simpre 21. (para nuestro  
ejemplo). y por eso lo importante del fixtemp en squeak y la mejora  
que significo Pharo.

cual se ejecuta,,, todos.... pero todos hacen lo mismo...

Espero ser claro....

PD: mariano ponele onda y traducilo.

Saludos

El 05/08/2009, a las 15:40, Mariano Martinez Peck escribió:

> Hi! I am trying to understand how seaside handle double or more,  
> request. I started with the simpler example: WACounter, which has:
>
> renderContentOn: html
>     Transcript show: 'renderContentOn'; cr.
>     html heading: count.
>     html anchor
>         callback: [ self increase ];
>         with: '++'.
>     html space.
>     html anchor
>         callback: [ self decrease ];
>         with: '--'
>
>
> increase
>     Transcript show: 'increase'; cr.
>     count := count + 1.
>     (Delay forSeconds: 3) wait.
>
>
> Now, suppose the counter is in 0. I click one time on '++' and wait  
> and I see in the transcipt:
>
> increase
> renderContentOn
>
> Ok, perfect. New session, 0 again. Now I click on '++' but before it  
> finish, I click 3 times more (very quickly). I can see this in the  
> transcipt:
>
> increase
> increase
> increase
> increase
> renderContentOn
>
> So, as I can see:
>
> 1) the callback (self increase in this case) is called for every  
> click.
> 2) the renderContentOn isn't call until all of the self increase of  
> that session finish.
> 3) when renderContentOn  is called, the webpage shows the number 1  
> (which is correct instead of 4).
>
> Now the questions are:
>
> a) how does seaside can do that? every request has its own  
> variables? I think this has to be with continuations but I want to  
> be sure.
> b) which of all of the self increase is the one that is finally  
> rendered? the first one?
> c) how can I handle the famous double commit? suppose now self  
> increase does something in a relational database (like persisting an  
> order or something like that) and I don't want it to get persisted  
> twice or I don't want an error because of duplicated PK.
>
> Thanks for the help. I just want to understand how this is handle!
>
> best,
>
> Mariano
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