Attachment URL

Introduction

In NocoBase, Attachment URL stores an external file access address.

It is suitable when files are already stored in an external system, object storage, or CDN and NocoBase only needs the access address. Use Attachment when NocoBase needs to upload and manage files, or URL for an ordinary web address.

Use cases

Attachment URL fields are suitable for these business scenarios:

• Files hosted in external systems
• Object-storage file addresses
• CDN image and document addresses
• External attachments referenced by business records

Create and configure

On the collection's Configure fields page, click Add field and select Attachment URL to create this field.

Setting	Description
Field interface	The field interface. Attachment URL uses attachmentUrl, which determines how the field is entered and displayed in pages.
Field display name	The name displayed for the field, such as File address, Image URL, or External attachment. Use a name that business users can recognize.
Field name	The field identifier used internally by APIs, relation fields, permissions, and workflows. It usually cannot be changed after creation. It supports only letters, numbers, and underscores, and must begin with a letter.
Field type	The data-layer type. Attachment URL uses string by default.
Default value	The default value. When a new record has no value, NocoBase can fill this value automatically.
Validation rules	Validation rules. Supports URL-format, length, and required validation.
Description	A field description. Record the field meaning, entry requirements, data source, or maintainer.

:::warning Note

Field names are referenced by page blocks, permissions, workflows, and APIs after creation. Confirm the name before creating the field to avoid later configuration changes.

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Field behavior

The default behavior of a Attachment URL field is as follows:

Behavior	Description
Default Field interface	attachmentUrl.
Default Field type	string.
Available Field types	string, text.
Page component	Uses an attachment-URL component for entry and display.
Filtering	Supports URL and text filters where supported by the data source.
Sorting	Supports sorting in Table blocks where supported by the data source.
Validation	Supports URL-format, length, and required validation.

Edit configuration

After creation, click Edit beside the field to edit its configuration. Edit fields to adjust how they are displayed and used in NocoBase, such as the display name, description, default value, validation rules, or field-specific settings.

When a field comes from a synchronized main-database table, editing usually maps the database field to a NocoBase Field type and Field interface.

Setting	Can be edited	Description
Field display name	Yes	Changes the name displayed in the interface without changing the field identifier.
Field name	No	The field identifier normally cannot be changed in the edit form after creation.
Field interface	Conditional	Main-database fields and synchronized fields can be adjusted during field mapping. Changes affect page input, display, and validation.
Field type	Conditional	Main-database fields and synchronized fields can be adjusted during field mapping. Confirm that existing values can be used by the new type first.
Default value	Yes	Adjusts the default value for new records.
Validation rules	Yes	Adjusts field validation rules.
Description	Yes	Adds the field meaning, entry requirements, data source, or maintainer.

:::warning Note

Changing a Field type or Field interface is more than changing a display name. It affects field storage, input components, validation rules, filters, and workflow-variable usage. When the field contains substantial existing data, confirm that its data format is compatible first.

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Delete field

Click Delete beside a Attachment URL field to delete it. You can also select multiple fields and delete them in the main data source.

Deleting a Attachment URL field created in the main database usually also deletes the actual database column and its values. For a synchronized or external-data-source field, the impact depends on the corresponding data source and field origin.

:::danger Warning

Deleting a field can affect page blocks, forms, filters, permissions, workflows, APIs, imports and exports, and existing data. Confirm that the field is no longer referenced by business configuration before deleting it.

:::

Use in pages

Attachment URL fields are suitable for external-file display, preview, and download.

Scenario	Use
Form block	Enter an external file address.
Details block	Display, preview, or download an external file.
Table block	Display external attachment values.
Workflows and APIs	Pass external file addresses to business logic.

Related links

• Fields - Learn about field categories and mapping.
• General collection - Create and manage fields in a collection.
• Attachment - Upload and manage files in NocoBase.
• URL - Store ordinary web addresses.