Work with variables, scripts, and expressions

26R1 reference · Documentation-based tutorial draft · Not executed in IFS

Treat variables as an interface

Document each variable’s source, type, scope, writer, consumer, and missing-value behavior. A matching name does not prove that two operations supply the same type.

Variable	Type	Written by	Read by
`ExternalReference`	Text or missing	Trigger mapping	Validation script
`referenceMissing`	Boolean	Script Task	Gateway
`relatedRows`	Collection	API Read Collection	Sequential subprocess
`deliveryReceipt`	Text	REST output mapping	Outcome check

Avoid the reserved ifsBpa prefix for your own variables. Internal variables are populated at particular stages; do not assume they exist at the start of every trigger type.

JavaScript task versus expression

A Script Task executes statements. An expression evaluates a value for a mapping or condition. Use the syntax belonging to the field you are editing.

Original script example:

var value = execution.getVariable('ExternalReference');
var cleanedReference = value == null ? '' : String(value).trim();
execution.setVariable('cleanedReference', cleanedReference);
execution.setVariable('hasReference', cleanedReference.length > 0);

Gateway expression:

${hasReference == true}

These are teaching fragments, not an assurance that every modern JavaScript feature is supported in the target engine. Prefer simple syntax and validate against the installed scripting runtime.

Inspect types as well as values

In Inspect, unquoted true is interpreted differently from the string "true"; True can be treated as text. Quoted numbers also differ from numeric inputs.

An internal enum such as ifsBpaProjectionOperation can be an enum in normal execution and a string in Troubleshoot. The documented comparison for that case uses value comparison:

execution.getVariable('ifsBpaProjectionOperation') == 'UPDATE'

This is a specific compatibility case, not a reason to remove type checks from every script. Test both inspection and the originating operation.

Mapping and scope checks

Task input/output mappings can introduce local values or overwrite existing values. Use different names for unrelated responses and ETags. User form IDs become variable keys, so reusing an ID can overwrite a value.

Capture a small execution and inspect the variable immediately before and after the task that is supposed to produce it. A variable existing at the end does not establish that it was available when a gateway evaluated it.

Failure cases to test

Test missing, null, blank, whitespace, normal, maximum-length, and unexpected-type inputs. For collections, test zero, one, and multiple items. For dates and timestamps, follow the time-zone guide rather than relying on a browser’s local parsing rules.

The first-validation template contains a pure decision script that can be checked locally. Local JavaScript tests verify its logic only; they do not reproduce IFS serialization, variable scope, grants, or transaction behavior.