[wxhaskell-users] Updating Choice controls with new content

[<chucky@dt...>]

Hi! I've been toying around a bit with wxHaskell lately and have run 
into a problem. My application needs to be able to add elements to a 
Choice control. The elements are read from a HaskellDB-based database as 
a list.

My question is this: When clicking my "add" button, how do I tell the 
Choice control to re-read its list from source? I'm assuming I need to 
send it some event, but which one?

Anders

Re: [wxhaskell-users] Updating Choice controls with new content

[Daan Leijen <daanleijen@xs...>]

Hi Anders,

On Wed, 16 Jun 2004 15:06:21 +0200, Anders H=F6ckersten <chucky@...=
mers.se> wrote:

> Hi! I've been toying around a bit with wxHaskell lately and have run in=
to a problem. My application needs to be able to add elements to a Choice=
 control. The elements are read from a HaskellDB-based database as a list.
>
> My question is this: When clicking my "add" button, how do I tell the C=
hoice control to re-read
>  its list from source? I'm assuming I need to send it some event, but w=
hich one?

I think you can just use the "items" attribute to set the form of the cho=
ice
control. Something like:

    c <- choice ...
    ...
    set c [items :=3D ["hi", "there"]]


Furthermore, I think you need to use the "dynamic" attribute on the
layout of the choice control.

    set f [layout :=3D .... dynamic (widget c) ... ]


I hope this helps,
All the best,
  Daan.


>
> Anders
>
>
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Re: [wxhaskell-users] Updating Choice controls with new content

[<chucky@dt...>]

Daan Leijen wrote:

> Hi Anders,
>
> On Wed, 16 Jun 2004 15:06:21 +0200, Anders H=F6ckersten=20
> <chucky@...> wrote:
>
>> Hi! I've been toying around a bit with wxHaskell lately and have run=20
>> into a problem. My application needs to be able to add elements to a=20
>> Choice control. The elements are read from a HaskellDB-based database=20
>> as a list.
>>
>> My question is this: When clicking my "add" button, how do I tell the=20
>> Choice control to re-read
>>  its list from source? I'm assuming I need to send it some event, but=20
>> which one?
>
>
> I think you can just use the "items" attribute to set the form of the=20
> choice
> control. Something like:
>
>    c <- choice ...
>    ...
>    set c [items :=3D ["hi", "there"]]
>
>
> Furthermore, I think you need to use the "dynamic" attribute on the
> layout of the choice control.
>
>    set f [layout :=3D .... dynamic (widget c) ... ]
>
>
> I hope this helps,
> All the best,
>  Daan.

That worked great! Thank you. Now, on to my next question, which is more=20
generally design oriented, but still touches the previous one. I have a=20
parent window, where you can open a child window to add some new data (a=20
customer in this case). When the new data has been saved, the Choice=20
control in the parent window has to be updated.

However, the child window has no specific knowledge of the Choice=20
control in the parent window, it only knows about the parent window, and=20
giving knowledge of the Choice control to the child window would break=20
encapsulation.

Is there any "recommended" way of solving these kinds of problems? Would=20
creating a new custom event, "updateParent" or similar be a good solution=
?

Actually, after having toyed with wxHaskell for a few days now how to=20
structure my code is my main problem. wxWidgets seems to force sort of=20
an object-oriented approach onto my Haskell program, which I am having=20
trouble adapting to. :) Still, I like wxHaskell. It works well and=20
produces nice results.

Regards,
Anders