Default operators with FA2 library in SmartPy

Question

I was wondering if, when using the FA2 library, there is a way to have the contract as a default operator so that users don't have to call update_operators ?

Thank you

Answer 1

Yes, you can do this by creating a new transfer policy.

Warning ⚠️ : having the contract be operator by default may introduce a security flaw or be totally fair depending on your contract's logic.

Here how to define a new policy:

import smartpy as sp
FA2 = sp.io.import_script_from_url("https://smartpy.io/templates/fa2_lib.py")


# Inherits from the OwnerOrOperatorTransfer policy
# but you can choose another base policy.
class MyPolicy(FA2.OwnerOrOperatorTransfer):
    # Explicitely change the policy name.
    # This whole method can be remove if you want to keep the base policy name.
    def init_policy(self, contract):
        FA2.OwnerOrOperatorTransfer.init_policy(self, contract)
        self.name = "this-contract-or-owner-or-operator-transfer"

    # Redefine the transaction transfer's permissions.
    def check_tx_transfer_permissions(self, contract, from_, to_, token_id):
        sp.verify(
            (sp.sender == sp.self_address)
            | (sp.sender == from_)
            | contract.data.operators.contains(
                sp.record(owner=from_, operator=sp.sender, token_id=token_id)
            ),
            message="FA2_NOT_OPERATOR",
        )

    def is_operator(self, contract, operator_permission):
        # Add self_address to is_operator (used in offchain view)
        return (sp.sender == sp.self_address)
               | contract.data.operators.contains(operator_permission)

Here how you set the policy as a named argument when instanciating your FA2.

c1 = FA2.Fa2<BaseClass>(..., policy=MyPolicy()).

Here is an example.