Ajax Callback Session Variable and Debugging

[chris.hazeslip]

Two part question:

1)How do i use a session variable in the ajax callback page? I have variable session.__protected__varname that i use on each page. i need to use this variable to add records to a table, however i cannot seem to access the variable from the callback page.

2) What is the best way to debug an ".ajax.a5w" page? It seems as though the only way i know something is wrong with a page is if nothing happens when i run it. e.g. Hit button "Submit", on page.a5w, that calls page.ajax.a5w. I should see a return of A or B no matter what, however I only know there is a problem if i see nothing.

[Steve Wood]

Re: Ajax Callback Session Variable and Debugging

I always have a couple rounds of debugging on making ajax callback pages. Any little error causes it to fail (appropriately).

Here is what I do, and it always comes down to isolating the problem:

I put save_to_file("got here", "c:\test.txt") at the top of the callback page just to see if it was called at all.

Then I change it to save_to_file(id, "c:\test.txt") assuming I am trying to pass a variable named id. At this point it often fails because I have an error on the calling side with my button or link.

Here is an example of a button with a callback. Notice I have a variable named "var". That's just a dummy so I can test that the value got over to my callback page.

Buy_render = "<input name=\"setvar\" type=\"button\" value=\"Add to Cart\" onclick=\"alert('Your item ("+Data.title+") was added');a5_AJAX_Callback('addtocart.ajax.a5w','var=abc&id="+data.id+"');\"/>"

You can also just execute your callback page directly by typing the full URL to your callback page. Often you will get a 500 error that explains what's wrong, whereas you get nothing if you call the page from your button.

Once I get it to work I document everything in my homegrown Help document and work from that known-good code.

Lastly, I often forget to put those three Javascript references in the Head area of the page with the callback button. I can test several dozen times before I realize I forgot that simple step.

[ColinJD]

Re: Ajax Callback Session Variable and Debugging

1)How do i use a session variable in the ajax callback page? I have variable session.__protected__varname that i use on each page. i need to use this variable to add records to a table, however i cannot seem to access the variable from the callback page.

I'm not 100% as to what your particular issue is.
-
In my case I would send the session.__protected__varname from the calling page to the AJAX page as a new variable
eg something like this

var theSessionProt  = <%A5 ?session.__protected__varname %>;

a5_AJAX_Callback('TheFile.AJAX.A5W','action=DoSumStuff&SendUp='+SendUp+'&theSessionProt='+theSessionProt);

Something I have found little info on is the built in AJAX Session management.
I have just started using my own home grown simple thread manager, and it's boosted the AJAX performance stacks, + saves notably on server performance.
-

What is the best way to debug an ".ajax.a5w" page?

Better to use some form of structered programming currently. Since AJAX and on A5 is in it's infancy, I don't think anyone has worked out how to properly do any debugging.

[Steve Wood]

Re: Ajax Callback Session Variable and Debugging

There's no need to send the session variable to the callback page; if it exists at the time the callback is made, the session variable already exists and can be used on the callback page just like any other page. There is nothing special about a callback page; it is just an A5W page like any other.

If you use Firefox's Firebug, there are some advanced ajax debugging tools there that work with Alpha. Check Alpha's release notes for some reference to "Firebug".

[chris.hazeslip]

Re: Ajax Callback Session Variable and Debugging

I was finally able to use my session variable in the afterFormValidate function. Any attemp to use the session variable during the onFormInitialize event failed, however.

Thank you all, for your help.

[StephenP]

Re: Ajax Callback Session Variable and Debugging

This doesn't work for all bugs, but it has helped me tremendously:

On the calling page, place a <span id=\"errorArea\"></span> at the top of the page. (Use span, rather than DIV because DIV causes an page break that will move your page down a line. SPAN will allow the area to remain unnoticed until needed.)

In your AJAX page, place the following:

at the very top:

<%a5
on error goto error_handler
? "$('error_area').innerHTML = '';"

at the very bottom:

end

error_handler:
    err = error_code_get()
    error_line = error_line_number_get()
    error_print = error_text_get(err)
    msg = "Error " + ut(str(err)) + ": " + error_print + " (line " + error_line + ")"
    ? "$('error_area').innerHTML = '" + jsEscape(msg) + "';"
    if error_text_get(err) = "Got this far" then
        resume next
    end if
end
%>

The IF statement with the "got this far" string is used when I can't figure things out. I can place a line like this:

error_generate("got this far")

in various locations throughout the code, and it will report the line numbers where they occurred. The "resume next" allows the code to continue running so you only see the last "error_generate" line and know that your error is after that line, but before the next "error_generate" line.

This has been very handy! In fact, you can place one every once in a while, and then comment them out to be user as needed by simply un-commenting them.

This has saved me a LOT of frustration. And it is important that it go at the top of your page, because you will often forget to look at the bottom to see if there was an error.

[ColinJD]

Re: Ajax Callback Session Variable and Debugging

Stephen,
I was just thinking Yesterday that there must be a way of doing this
Thanks, I'm sure you have saved me a stack of work
Regards
Colin