[Bese-devel] Follow up to "New tutorial typos"

[burban at opopop.net]

szergling <senatorzergling at gmail.com> writes:

[...]

> 
> Now, I am also confused about another thing. Suppose a component
> displays an action that does not 'answer', but has side-effects
> instead. I'm not sure why this action would repeatedly get called even
> when the component display is only refreshed and not clicked on.
> 
> Here is a simple example to illustrate:
> 
> (defcomponent refresh-demo ()
>   ((value :initform 0
>           :accessor component-value)))

Add slot option ":backtrack t" for value.
Works also for the <ucw:form variant below.

> 
> (defmethod render ((c refresh-demo))
>   (<:p "Current value is: "
>        (<:as-html (component-value c)))
>   (<ucw:a :action (incf (component-value c))
>        "Increase value"))
> 
> (defentry-point "refresh.ucw" (:application *example-application*)
>     ()
>   (<:p "Refresh test")
>   (call 'refresh-demo))
> 
> 
> It is similar to the counter (increment/decrement) example. We have a
> value which can be increased by clicking on our incf action. After the
> first click on the hyperlink, I see a new incremented
> value. Subsequent clicks on the hyperlink also increment the value, as
> expected. However, clicking on "refresh" in my browser (after the
> first increment action) also results in the value being incremented. I
> expect to see the same value, since no action has been carried out,
> really.
> 
> I can sort of see why this must be so I guess, since there's some "URL
> propagation-like" stuff, so even a refresh is a new "hit" causing an
> action. However, this also works with form actions, and seems wrong,
> since nothing has been posted...
> 
> (defmethod render ((c refresh-demo))
>   (<:p "Current value is: "
>        (<:as-html (component-value c)))
>   (<ucw:form
>    :action (incf (component-value c))
>    (<:input :type "submit" :value "Increase value")))
> 
> Again, try to increment once (clicking on the form button), then just
> use refresh. So what have I done wrong here? Would appreciate any
> pointers.

Well, time for a new chapter of the tutorial "backtracking":)

-- 

B. Urban