What It Does

For every field in JCB, you can configure rule-based behaviors visually. This avoids hand-coding and ensures your field:

• Behaves correctly in forms (e.g. required fields trigger validation)
• Generates accurate database constraints (e.g. unique columns)
• Applies correct save/load logic for null values or defaults

These GUI-defined rules are enforced during both compilation and runtime, streamlining consistency between what users see and how data is handled in the backend.

Key Rule Options

• ✅ Required: Marks the field as mandatory in the edit view form. JCB auto-generates validation checks and ensures submission cannot proceed unless the field is filled.
• 🔁 Unique: Ensures the field’s value is not duplicated across records. JCB injects uniqueness validation logic into the model or controller during compile.
• 🚫 Nullable: Controls whether a database column can accept NULL. When unchecked, the field always stores a default or zero value.
• 🎯 Default Value: Specify a default for new records. JCB writes this to the SQL schema and loads it into the form unless overridden.
• 🛡️ Readonly / Disabled: Useful for fields that should be displayed but not modified in some contexts (e.g., generated slugs, system values).
• 🔐 ACL-Aware: Each rule can respect Joomla permissions. You can make fields required only for certain user groups or editable only under specific access conditions.

Where It’s Configured

• Inside the Field configuration form (in the Rules/Validation tab)
• As part of the Field Type definition (to enforce defaults)
• In View configuration (to override global rules per context)

Use Cases

• ✅ A required title field on every form
• ✅ A unique email address field for each user record
• ✅ A nullable expiration date field with optional input
• ✅ Setting defaults for boolean switches or dropdowns
• ✅ Disabling certain fields during record editing based on user group

Conclusion

JCB’s GUI-driven rules framework saves you time, ensures consistency, and removes repetitive code. Whether you're enforcing data integrity or building smart forms, these field-level constraints let you bake business logic right into the structure of your component — visually and declaratively.