How to calculate fields in a form?

Question

Hello,
I am new to apex and i have a question about create a simple calculation in a form.
I created a form and i have 3 fields which i want to use for calculating.
Field 1/ field 2 = field 3
when the user enters data into the first and second field it will automatically calculate the third field.
How can i do this?
i am using
Application Express 4.2.1.00.08

Answer 1

The short answer is that it depends. I'm assuming you want the calculation to appear as soon as the second value is put in, and if this is the case then javascript is the answer. You can create a generic javascript function that does division and takes to input parameters and returns the result. Inside the function you would check to make sure the denominator isn't zero (an illegal operation), do the math and assign the calculated value to the return value of the function.
The function code would look something like this:
function div_values(numerator, denominator) {
// pass page item names into the function
// $v will get the value from the item name
if ($v(denominator) != 0) {
result = $v(numerator)/$v(denominator);
return result;
}Then you can call the function via a dynamic action by selecting a "Javascript Expression" for a Set Value operation (Advanced dynamic actions) and put this into the Javascript expression area:
div_values(P1_NUMERATOR,P1_DENOMINATOR)
The reason I recommend creating this little function as opposed to just doing the math in the javascript expression area is that the function becomes reusable and the page items aren't hard coded into the function. Then you can use the function wherever you want to on the page or, if you put it in a place where every page can get to it, you can use it anywhere in the app.
Earl