Best Practices for checking/adding/removing operators for a user's FA2 tokens with regarding to allowing a contract to take actions on said tokens

Question

I'm trying to call an entry-point in a contract that will manipulate a user's tokens and am wondering what are the best practices for adding/removing operators to a user’s FA2 tokens?

I need to add a contract as the operator of a user’s tokens and am wondering the best way to go about it. Couple of cases I am considering:

1. Should the call to update_operators only happen if the contract isn’t yet an operator of the users yet? I try to call an entry-point function in the contract and if I get the FA2_NOT_OPERATOR error then I call the update operators and retry the entry-point afterward

2. Should the call to update_operators happen before every entry-point function contract call without removing the operator after the operation is complete?

3. Should the call to update_operators happen twice, before and after the entry-point function contract call? First to add the operator and then to remove it?

Answer 1

You can call the:

1. update_operators (add_operator)
2. do your transaction
3. update_operators (remove operator)