Re: [Fxruby-users] DataTargets, and more about messaging.

[Hugh S. S. E. E. <hg...@dm...>]

On Sat, 14 Jun 2003, Lyle Johnson wrote:

> If memory serves, Jeroen has added a clear() method for FXTextField in
> FOX 1.2, but you're correct that it's not there for FOX 1.0. You would
> just need to set the text field's text to the empty string, i.e.
>
>      aTextField.text = ""

OK, that makes sense...
>
> OK, so focusing on the SEL_COMMAND handler block for @clear_button, I
> can see a few things that are definitely wrong. Back at the top of the
> LoginWindow#initialize method, you set @user as follows:
>
>      @user = FXDataTarget.new("")
>
> and so @user holds a reference to a FXDataTarget instance. So far, so
> good. But the first line of the SEL_COMMAND handler for @clear_button is:
>
>      @user = ""
>
> which constructs a new String, and assigns it to @user (this is just

DOH! Good point, I was forgetting this fundamental aspect of ruby!
<blush/>

        [...]
> that data target object). The next line:
>
>      @username.text = ""
>
> is a good guess, and I wish it would have worked (but I know why it
> doesn't). I'll come back to that in a moment. The next line:
>
>      @username.handle(@clear_button, SEL_CHANGED, "")
>
> is also a good guess, but more complicated than you would want. If you
> did want to take this route, though, you'd need to fix the second
> argument to handle() so that it includes both the message type and
> message identifier, e.g.

Yes, I thought that was probably part of it, since the last
correpsondence...
>
>      @username.handle(@clear_button, MKUINT(0, SEL_CHANGED), "")

Yes, I've seen things like this in the C++, but this reads to me
like "make an unsigned Int of (0,SEL_CHANGED)" so the "magic" must
lie in that first parameter?  Would you have a ref to point me at
for this, please?  I may not need the details now given the info
below, but it would be good to understand.

>
> But again, this looks ugly, and there's a better way.
>
> When you've attached a data target to one or more widgets and want to
> update the value of that data target programmatically (e.g. resetting
> the string to the empty string), you want to use the FXDataTarget#value
> accessor methods. So for your case, you should be able to write the
> SEL_COMMAND handler for @clear_button as follows:
>
>      @clear_button.connect(SEL_COMMAND) {
>          @user.value = ""
>          @pass.value = ""
>      }

That is a lot nicer.  Thank you.  And hence this is not .text
because it is not the GUI element that is being changed.
>
> Hope this helps,
>
> Lyle
>
>
        Thank you,
        Hugh