Callbacks
Callback functions are based on the event dispatcher pattern. You can register one or more callbacks for a certain event and when the event is triggered, the callback functions are being executed. Callbacks allow you to customize the program flow of the Contao core engine.
Global callbacks
| Callback | Description |
|---|---|
| onload_callback | Is executed when the DataContainer object is initialized. Allows you to e.g. check permissions or to modify the Data Container Array dynamically at runtime. |
| onsubmit_callback | Is executed when a back end form is submitted. Allows you to e.g. modify the form data before it is written to the database (used to calculate intervals in the calendar extension). |
| ondelete_callback | Is executed before a record is removed from the database. |
| oncut_callback | Is executed after a record has been moved to a new position. Added in version 2.8.2. |
| oncopy_callback | Is executed after a record has been duplicated. Added in version 2.8.2. |
Listing callbacks
| Callback | Description |
|---|---|
| paste_button_callback | Allows for individual paste buttons and is e.g. used in the site structure to disable buttons depending on the user's permissions (requires an additional command check via load_callback). |
| child_record_callback | Defines how child elements are rendered in "parent view". |
| group_callback | Allows for individual group headers in the listing. |
| label_callback | Allows for individual labels in the listing and is e.g. used in the user module to add status icons. |
Operations callbacks
| Callback | Description |
|---|---|
| button_callback | Allows for individual navigation icons and is e.g. used in the site structure to disable buttons depending on the user's permissions (requires an additional command check via load_callback). |
Field callbacks
| Callback | Description |
|---|---|
| options_callback | Allows you to define an individual function to load data into a drop-down menu or checkbox list. Useful e.g. for conditional foreinKey-relations. |
| input_field_callback | Allows for the creation of individual form fields and is e.g. used in the back end module “personal data” to generate the “purge data” widget. Attention: the field is not saved automatically! |
| load_callback | Is executed when a form field is initialized and can e.g. be used to load a default value. |
| save_callback | Is executed when a field is submitted and can e.g. be used to add an individual validation routine. |
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