Database Driver

Kanun uses a pluggable database driver for exists and unique rules.

Why a Driver?

The validation package stays framework-agnostic and does not hard-couple to a specific ORM/query builder.

Registering a Global Driver

import { IDatabaseDriver, Validator } from 'kanun';

class AppDatabaseDriver extends IDatabaseDriver {
  async exists({ table, column, value, ignore }) {
    const row = await db.table(table).where(column, value).first();

    if (!row) return false;
    if (ignore != null && String(row.id) === String(ignore)) return false;

    return true;
  }
}

const driver = new AppDatabaseDriver();

Validator.useDatabase(driver);

Registering Per Validator Instance

const validator = new Validator(data, rules).database(driver);

Using with Rules

const validator = new Validator(
  { username: 'legacy', email: 'john@example.com' },
  {
    username: 'unique:users,username',
    email: 'exists:users,email',
  },
);

How unique Works

Kanun calls driver.exists(input) for both exists and unique rules.

• exists passes when exists(input) returns true
• unique passes when exists(input) returns false

Rule Parameter Format

• exists:table,column
• exists:connection.table,column
• exists:table,column,ignore
• unique:table,column
• unique:connection.table,column
• unique:table,column,ignore

Driver Input Shape

The exists(input) method receives:

• table
• column
• value
• ignore (optional)
• connection (optional)
• attribute (optional)
• data (optional full request payload)

See Database Driver Contract for types.