Form Button and JavaScript Access Session Variables

[springguy]

Looking for general understanding/approach.

If you have a button added to a form, and when the button is clicked, you want to do some local analysis of a variable and if there is a problem with the variable data, popup an error, otherwise call a procedure or web page.

What is the best strategy for that?  Is it to call javascript before the OnClick procedure or URL call?  If so, how does the javascript access the variable NT data?  A simple, conceptual example would be helpful.

Or, is a better strategy to call a source procedure on the OnClick and depending on the clarion code there, call the appropriate procedure or web site?

Mike

[Bruce]

Hi Mike,

>> If you have a button added to a form, and when the button is clicked, you want to do some local analysis of a variable and if there is a problem with the variable data, popup an error, otherwise call a procedure or web page.

This is such a common question, but unfortunately you've got it the wrong way around. Decisions are made in the _browser_ not on the server. The poppping-up-an-error is ok. To change the page you'd do something like;

p_web.Script('href.location="somepage"')

I'm not sure what you mean by "call a procedure" - the context of that you need to explain more.

Cheers
Bruce

[springguy]

Thanks Bruce.

I have a specific case where I have a form with an added button.  The purpose of the button is to send an email based on information in the form data.  Using example 11, this was pretty straightforward, and works well.

However, if a data variable in the record has a certain value, then I do not want to send an email, but would rather popup a message telling the user why they cannot send an email, and then return to the form.

What I have been forced to do at the moment is to disable the button if the field value has that certain value.  That's workable, I guess, but it requires the user to understand why it is disabled, rather than the system telling them why.

So, what I am trying to get straight is when I click an added button on a Form, what is the best approach in general to do the following:

1. interrogate a variable on the record (or in a session variable)

2. have code (JavaScript I assume) that, on the basis of the variable contents, will popup a message within the browser, or...

3. call a different NT procedure or web page to do the analysis and action taking.

I don't know anything about JavaScript (yet, I suppose) to know if doing something like interrogating a value and calling for one of a multiple set of actions is possible - I assume it is, but how, and is that the best approach?

OR, is it a better approach (for us clarion guys) to have the button click call a NT source procedure that will interrogate a variable and then have it take one of a series of actions?

OR, is there a different, better approach that you would recommend. 

I would not be surprised that this is a pretty common question for us clarion guys, and I am slowly getting a better understanding of the "web programming" evironment of NT, but can you give us some practical guidance on how to interrogate a variable on a form when an added button is clicked and take a variety of actions depending on the value in the variable (ie popup, go to a NT procedure, go to a web page, etc).

Does that help clarify?
Mike

[Bruce]

Hi Mike,

>> can you give us some practical guidance on how to interrogate a variable on a form when an added button is clicked

The form value is in the session queue at that point.

>> I have been forced to do at the moment is to disable the button if the field value has that certain value.  That's workable, I guess, but it requires the user to understand why it is disabled, rather than the system telling them why.

that's what "comments" are for. You can set the comment of the button to explain why it is disabled.

Cheers
Bruce

[springguy]

Bruce,
I really appreciate your comments over the weekend.

I do understand that the values are in the session queue.  I think what I am asking is "can JavaScript access those values, and if so, can you give a simple example of what a piece of JS code would look like that does access a session value". If that is possible, then it opens an interesting door of possibilities in client side dynamics. 

Regarding using the comments to explain a situation, I had never thought of that as being a dynamic set of comment.  Thanks for the suggestion - I think I can run with that.
Mike

[Bruce]

>> can JavaScript access those values,

no, not directly of course. the values are on the server side. To get the current value of one of them, the browser could "ask" (as in make an asynchronous request) and perhaps you have a web page that'll return that value - but there's no "GetSessionValue" function.)

also the request would be asynchronous, so it would be somewhat harder to use unless you were familiar with JavaScript callbacks etc.

cheers
Bruce

[kevin plummer]

Hi Mike,

If you are just starting out in the web I wouldn't be too quick to jump in and start trying to use Javascipt. For the most part NTW protects us from that big bad world which makes the learning curve much easier. In your case the way I see it is you have 2 options. One, disable the button and use the comments field or insert a field to let the user know why the button is disable and enable the button when everything is good. Two, create a popup error form. Set the URL on your button to be dynamic (a GSV) and update this variable to be either the popup form or your email procedure. The caveat is if you can popup a form from a button from the templates. I hand coded this in NTW5 and without template support would be too complicated to work out.

Cheers,

Kev

[springguy]

Thanks Bruce and Kevin,
I really appreciate your advice.
Mike