Generate a value in first OnGridExecute and re-use it in future callbacks. Session variable no good as 2+ tabs can be open.

[dorobe]

Hi all,

I'm using a session variable to filter grids throughout the application; this variable can be set from a drop-down menu at the top of almost any page in the application. In the OnGridExecute event I am checking the session variable and, based on this, modifying the value of e.rv.tmpl.CS.SQL to get the dataset I need. This works fine most of the time but if a user opens two tabs and changes the session variable in the second, returning to the first and (for example) searching the grid or changing it's page will cause OnGridExecute to change the grid's dataset; once a page has been loaded I want it to keep using the filter it started with.

I first tried storing values for re-use in the e and rtc objects, but these were not preserved between callbacks. I then tried using e._state and found this wiki page which explained why my method wasn't working and appeared to present a solution; however, it doesn't seem possible to cause an AJAX response from OnGridExecute using the method described (can anyone confirm this? I couldn't get a simple JavaScript alert to be returned).

I'm now feeling a bit stuck on this, so any help would be greatly appreciated. Preferably I'm looking for a solution which only requires I make changes in OnGridExecute as I will need to update a large number of pages once a solution is found, ultimately though I just need a way of preserving a variable between callbacks from the same page.

Thanks for reading,
dorobe

[mvaughn]

Re: Generate a value in first OnGridExecute and re-use it in future callbacks. Session variable no good as 2+ tabs can be ope

Hi dorobe,
As long as we are talking about two different grids on two tabs you make specific session variables for each.

Grid A uses SESSION.VALUE1 = statement
Grid B uses SESSION.VALUE2 = statement

[dorobe]

Re: Generate a value in first OnGridExecute and re-use it in future callbacks. Session variable no good as 2+ tabs can be ope

Hi Michael - and thanks for taking the time to respond to my post.

Unfortunately this wont work for me as the user can have the same grid open in multiple tabs (and I should say here that by tabs I mean browser tabs, not tabs in an Alpha Grid; I wasn't aware these existed when I first posted). When the user makes a selection from the drop-down box on any page a session variable is set so that all grids then opened (on a new tab or by refreshing the page) will display data relevant to their selection then the browser tab that the user made the selection on refreshes. Any other open tabs however will not be refreshed and so continue to display data relevant to the previous selection (this is desired behaviour) but any grid in these tabs that makes an ajax callback will then switch over to displaying data relevant to the new selection (not desired behaviour).

If I could set a variable local to the browser tab from the OnGridExecute event the first time it runs and then refer to that in subsequent callbacks it would be perfect, but I can't find a way to preserve a variable between callbacks or include my own JavaScript instructions in the Grid's ajax response. I'm sure the functionality I'm looking for must exist within Alpha but I'm really struggling to find it.

Any ideas?

Thanks again for getting back to me,
dorobe

[mvaughn]

Re: Generate a value in first OnGridExecute and re-use it in future callbacks. Session variable no good as 2+ tabs can be ope

Perhaps you can refresh the grid on a pulldown selection. I'm thinking OnChange. That way the grid gets refreshed each time a new selection is made.

[agillbb]

Re: Generate a value in first OnGridExecute and re-use it in future callbacks. Session variable no good as 2+ tabs can be ope

Recheck that wiki page that you posted (in your first post) again - steps 1 and 2 are useful.

In your OnGridExecute (serverside) event, maybe you could check eval_valid("Request.Variables.__si2.myvar1") to see if your chosen variable exists.
If it does, then use it. If it doesn't, then use the session variable's value.

Then use the afterAjaxCallback clientside function to set a stateInfo grid variable ONLY if it doesn't exist.
var si = {grid.object}.stateInfo;
si.myvar1 = 'new value for myvar1';

I haven't tried it, but it seems like a reasonable enough approach.

Andy.

[dorobe]

Re: Generate a value in first OnGridExecute and re-use it in future callbacks. Session variable no good as 2+ tabs can be ope

Thanks both of you for your replies - this is really helpful stuff.

mvaughn - I'm currently refreshing the whole page when the drop down is used but other open browser tabs don't refresh (and I don't want them to as the user should be able to see two selections side by side if they want to). The pages have the current selection included in the html by Alpha so it is clear to the user which selection was in use when the page was loaded, however since the ajax callbacks are currently using the session variable they can go out of sync with the static part of the page.

agillbb - I think you're on to something here, and it looks like maybe I'm over-complicating things by trying to do everything from OnGridExecute. My time on this project is pretty slim at the moment as a higher priority job has come in but hopefully there will be an opportunity to test this out tomorrow. I'm going to try using one of the early clientside events (the ones that fire when the grid first loads) to set that variable right away as (I believe) session variable values are accessible to the JavaScript on clientside. I'll post back what I did if it works for future readers.

Thanks again,
dorobe

[dorobe]

Re: Generate a value in first OnGridExecute and re-use it in future callbacks. Session variable no good as 2+ tabs can be ope

Ok - I didn't get the to try this again until today but good news - it's working!

My thanks to both of you. :)


In case anyone comes across this page later with a similar problem, here's what I had to do:
- Publish Session variables for the grid (explained here for dialogs, but it works the same way)
- Use the code Andy suggested above where "new value for myvar1" is replaced with {grid.object}._vars.SESSION.VARIABLE_NAME_IN_CAPS
- I put the client side code in onGridInitializeComplete instead of afterAjaxCallback so that it only runs once (I was hoping to use an event which fires before OnGridExecute but the session variable doesn't appear to become available on client-side before then)
- In OnGridExecute I check if either the Request or Session variable exists (prioritising the Request variable) and if so use that value in the WHERE clause of e.tmpl.CS.SQL (first converting to numeric and back with STR() and VAL() if using the Request variable to protect against SQL Injection). If neither exists I use SELECT TOP 0 * FROM table WHERE 1 = 0 in my SQL to ensure nothing is returned.

It was that simple all along!

Thanks again,
dorobe