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Variable Creator JSON Reference

IVariableCreator is a shared JSON object contract used in multiple workflow settings.

You see this shape in places like:

  • HTTP receiver QueryStringParameters values
  • HTTP receiver UrlSections entries
  • variable-creation transformer metadata

This page defines the JSON object shape and behavioral implications.

Core object shape

Minimal interface-level shape:

{
  "VariableName": "patientId",
  "SampleVariableValue": "12345",
  "SampleValueIsDefaultValue": false
}

Extended concrete shape (when VariableType is present):

{
  "VariableName": "patientId",
  "SampleVariableValue": "12345",
  "SampleValueIsDefaultValue": false,
  "VariableType": 0
}

Fields

Field Type Required Meaning
VariableName string yes Variable key name used in workflow.
SampleVariableValue string optional Example/default-like value used for binding context and optional initialization behavior.
SampleValueIsDefaultValue boolean optional If true, consumers that support initialization may pre-seed the variable using SampleVariableValue.
VariableType integer enum optional Variable category metadata when concrete VariableCreator shape is serialized.

VariableType values:

  • 0 = Workflow
  • 1 = System
  • 2 = Global

Behavior notes by common usage

HTTP receiver query parameters / URL sections

In these contexts, SampleValueIsDefaultValue is operational:

  • default value can be initialized before inbound request values are applied
  • missing/empty inbound values may leave the initialized default in place

Transformer variable metadata

In transformer contexts, SampleVariableValue and SampleValueIsDefaultValue are mostly metadata/binding aids.

Runtime value assignment usually comes from transformer source evaluation, not from sample initialization.

Non-obvious outcomes

  • VariableName is the actual runtime key; keep names stable and consistent with ${VariableName} usage.
  • VariableType is not part of the core IVariableCreator interface but can still appear in serialized objects that use concrete VariableCreator.
  • SampleVariableValue is often treated as design-time context unless the host setting explicitly uses initialization logic.
  1. Keep VariableName explicit, stable, and unique within the same logical variable scope.
  2. Use literal sample values only; do not embed paths as sample values.
  3. Set SampleValueIsDefaultValue = true only when a real default-initialization behavior is intended in that specific setting.
  4. Use VariableType = 0 unless you explicitly need System or Global category metadata in that context.

Examples

Query string parameter variable descriptor

{
  "VariableName": "siteId",
  "SampleVariableValue": "main",
  "SampleValueIsDefaultValue": true,
  "VariableType": 0
}

URL section variable descriptor

{
  "VariableName": "patientId",
  "SampleVariableValue": "12345",
  "SampleValueIsDefaultValue": false,
  "VariableType": 0
}