Overview

Validations

Custom validation rules on fields, forms, and application flows.

manual__validations__01.png: Validation tab (upper part) in the column metadata editor.
manual__validations__02.png: Validation tab (lower part) with custom script and type validation.
manual__validations__03.png: runtime example in a form with unfilled required fields.

mc_validation_required: makes the field mandatory in edit/insert.
mc_validation_required_message: custom message for required (tooltip/error near the field).
mc_validation_pattern: validation regex (executed client-side on the field value).
mc_validation_pattern_message: custom message when the pattern is not met.
mc_validation_max_length: maximum allowed length.
mc_validation_max_length_message: custom message for exceeding max length.
mc_validation_min_length: minimum required length.
mc_validation_min_length_message: custom message for min length not met.
mc_validation_custom_callback: custom validation script (typical signature: record, field, vr, wtoolbox), used for business rules not expressible with standard constraints.
mc_validation_type: typed validation (e.g., email/url/number/date depending on supported types in the build).
mc_validation_type_message: custom message for type validation error.
mc_value_change_trigger_event: hook on value change, useful for triggering recalculations or dependent validations between fields.

In the form, required fields are marked with *.
If the field does not pass the rules, an error indicator is shown with the message configured in the metadata.
Rules are applied before saving, reducing unnecessary roundtrips to the server.
Custom validations allow conditional logic based on the current record and UI context.

Use custom messages to make errors understandable for the end user.
Avoid overly aggressive regex on lookup or auto-formatter fields.
For complex cross-field rules, prefer mc_validation_custom_callback over long and hard-to-maintain patterns.