Canister guard in Rust on the Internet Computer
I recently discovered it was possible to specify a guard function to be executed before update and query functions of canister smart contracts written in Rust on the Internet Computer.
You might tell me that the following post is just a rip off of the Crate documentation but, as I only figured out this was possible while having a look at the transaction notifier repo of OpenChat, I thought it was worth a post 😄.
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Original approach
I began my journey with Rust when I migrated my existing Motoko code — i.e. when I upgraded the existing smart contracts of Papyrs.
As these canisters were dedicated to user data, I had to migrate functions that required access control too.
For this purpose, I implemented comparison of principals — i.e. I match the callers of functions against users that are saved in the state. If they are equals, methods can be executed, if not, I throw errors and reject the call.
