A5.ajax.callback Method

Syntax

A5.ajax.callback(url,data)

Arguments

urlstring: The URL of the .a5w page that will handle the callback
datastring: The value pairs to send back to the page. These are the values that would be seen after the "?" in a URL, commonly referred to as the GET or query string. This parameter should have the same syntax as any GET.

Description

Makes an Ajax callback to the server.

Discussion

It is often desirable to make a call back to a server side page to return some value or action, and there is no need to actually submit a form element. The A5.ajax.callback() method allows sending values back to a page for processing.

For example, a common need is to send a couple values back to the page to tell the page that some action must be taken and there are some values available for that action. The URL is the callback page, and the data includes any values to meet that need.

For example, consider a code page named "calculatesale.a5w" contains some Xbasic code to populate a control named 'salestax'. To do this, it needs to be told to run that code section, and send along a value for state to determine what tax table to use. The call back function call could be:

A5.ajax.callback('calculatesale.a5w','action=gettaxtable&state='+$gvs('state_ID'))

Prefer to use the {dialog.object}.ajaxCallback() or {grid.object}.ajaxCallback() methods when possible.

In this example, the state value was in a control with an ID attribute of 'state_ID'. The function $gvs() is a function the core.js Javascript library to harvest the value in the control. It is similar to document.getElementById(), but will harvest a value from any control by ID or name.

The page "calculatesale.a5w" may have some code similar to:

dim __formAction as c = default ""
dim action as c

if (__formAction = "Submit") then 
    if  onFormValidate(local_variables())
         afterFormValidate(local_variables())
    end if
else if (__formAction =  "Initialize") then 
    onFormInitialize(local_variables())
else if (action  = "gettaxtable") then
    gettax_table(local_variables())
end  if
 
function gettax_table as l(vars as p)
    with vars
        if (variable_exists("state") = .f.) then ' the state value was not sent
            'can't  evaluate, quit
            exit function 
        else if (state = "") then
            'state has no  value, can't evaluate, quit
            exit function
        end if

        ' ok, all values  known - do something
    end with
end function