A couple of weeks ago, I started a series of posts on FormCalc Expressions. The first ones I convered were the If and For expressions. This time, I thought I would explain the Foreach expression.

Foreach Expression

The Foreach expression is quite similar to the For expression but is meant to be used to achieve a slightly different kind of iteration that may be better suited to your needs rather than just increasing/decreasing the value of a counter (as for a regular For expression). The difference is that the Foreach expression assigns a different value taken from an argument list (list of objects/values) to a variable for each iteration of the loop (and there’s one iteration for each argument in the list).

FormCalc Syntax

foreach Variable in (ArgumentList) do
  ExpressionList
endfor

In this syntax, there’s an ArgumentList. This is simply a comma-separated list of objects/values to assign to the Variable on each iteration.

Based on the syntax, you can do things like set a total field’s value to the sum of subTotal, shipping and taxes fields:

foreach val (subTotal, shipping, taxes) do
  total = total + val
endfor

In this example, each time the expression loops, the variable val assumes the “identity” of a different object in the argument list: First, the subTotal field, then the shipping field and, finally, the taxes field.

JavaScript Syntax

For comparison, here is the equivalent JavaScript examples (note the semicolons and curly braces):

var arr = {0: subTotal, 1: shipping, 2: taxes};

for (key in arr)
{
  total.rawValue += arr[key].rawValue;
}

(In this case, the curly braces are optional but I think this is better style.) It’s certainly more cumbersome in JavaScript using the For…In expression (which is the closest equivalent to FormCalc’s Foreach expression I could find) because it’s only meant for iterating through an object’s properties or an array’s keys (which is what my example is doing).

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Posted by Stefan Cameron on October 7th, 2006
Filed under FormCalc,Scripting
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