FHIRPath Expressions with visual editor

The article describes how to write FhirPath expressions for calculations, enable-when logic and population using the FHIRPath visual editor

The FHIRPath Expression visual editor is a tool designed for non-technical users working with electronic medical forms based on the FHIR Questionnaire resource. It offers a low-code environment for creating, editing, and testing FHIRPath expressions that support dynamic behavior, calculations, data population, and named expressions within forms.

Key Use Cases:

  • Enable or disable fields dynamically

  • Calculate values (e.g., scores, age, BMI)

  • Pre-fill form fields using existing data

  • Define and reuse named expressions

How to Use the FHIRPath Visual Editor

1. Create an Expression

After creating the form and adding a set of fields:

  • Navigate to the Rules section of the field where you want to apply logic.

  • Select one of the expressions: Enable-when, Calculated, or Population.

  • Click Visual Mode to open the FHIRPath Expression Editor.

  • Set any variables (named expressions) you want to use in the expression.

  • Write your final FHIRPath expression using the editor interface.

2. Test and Debug an Expression

After writing your expression:

  • Fill out the form as a user would.

  • Open the Debug Console to test and debug how your expression behaves with actual data.

  • Close the FHIRPath Editor panel when you're finished. Any expressions you've written are saved automatically into the Questionnaire resource.

Validation and Error Handling

  • Automatic Validation: FHIRPath expressions are validated in real time.

  • Error Highlighting: If there are issues with syntax or logic, errors will be highlighted directly in the editor for easy correction.

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