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Creating controllers

Understand how to create a controller contract.

This page highlights a few examples of how to create a controller contract in Solidity.

"Allow all" policy​

Default ownership grants the owner the following "allow all" abilities to only the owner, but a custom controller could enable this for anyone:

  • allowInsert ⇒ true Allow INSERTs into the table.
  • allowUpdate ⇒ true Allow UPDATE on all columns.
  • allowDelete ⇒ true Allow DELETE, including using WHERE statements.
  • whereCheck ⇒ "" Defaults to an empty string, meaning, no WHERE clause additions are implemented.
  • withCheck ⇒ "" Defaults to an empty string, meaning, no CHECK clause additions are implemented.
  • updatableColumns ⇒ new string[](0) Defaults to an empty list, meaning, there are no restrictions on which columns can be updated.

In other words, if a custom TablelandController contract has not been set, the default values for the Policy are those defined above.

"Allow none" policy​

Similar to the example above, you could choose to disable everything by setting false or empty values:

ITablelandController.Policy({
  allowInsert: false,
  allowUpdate: false,
  allowDelete: false,
  whereClause: Policies.joinClauses(new string[](0)),
  withCheck: Policies.joinClauses(new string[](0)),
  updatableColumns: new string[](0)
});

Example implementation​

The following example shows how to import the ITablelandController interface and then create a policy that only allows INSERTs on a table, from any address.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.12;

import "@tableland/evm/contracts/ITablelandController.sol";
import "@tableland/evm/contracts/policies/Policies.sol";

contract ExamplePolicy {
  function getPolicy(address sender)
      public
      payable
      override
      returns (ITablelandController.Policy memory)
  {

    /*
    * Add any custom ACL check here, like token ownership.
    */

    // Return allow-insert policy
    return
      ITablelandController.Policy({
        allowInsert: true,
        allowUpdate: false,
        allowDelete: false,
        whereClause: Policies.joinClauses(new string[](0)),
        withCheck: Policies.joinClauses(new string[](0)),
        updatableColumns: new string[](0)
      });
  }
}

Alternatively, you could lock down your table to "allow none" for now, and then unlock your policy with a modification later. A dynamic policy could be interesting in cases such as post-reveal during your NFT launch.