Motoko actor class canister id

Developers Motoko
1

Currently if we want to access current canister id in nested modules we need to pass canister id as init arg:

shared ({ caller }) actor class Canister(canisterId : Principal) {...

Would be helpful if we could access the canister id like this:

shared ({ caller; canister }) actor class Canister() {...

here canister : Principal

What do you think?

2

If you want the self reference of the resulting actor, we have a syntax for that:

actor class Client() = self {
  ...
}

EDIT: Ah, I see you want the creator of the new canister. I don’t think that is conveyed by the protocol. But you can probably get hold of the controllers list.

3

In this case I cannot get canister id anywhere other than inside that actor class.

For example I want pass current canister id to class or func from another file:

// a.mo
class A1(x : actor{}) {};
class A2(x : Principal) {};
class A3(x : () -> Principal) {};

// main.mo
actor class Client() = self {
  let a1 = A1(self); // error "cannot use self before self has been defined"
  let a2 = A2(Principal.fromActor(self)); // error "cannot use self before self has been defined"

  func getCanisterId() : Principal = Principal.fromActor(self);
  let a3 = A3(getCanisterId); // error "cannot use getCanisterId before self has been defined"
}

No, creator is caller in that example.

4

I recall discussing this cannot use self error with @claudio earlier. IIRC we concluded that this is a definedness analysis bug (infelicity) in Motoko, and the self binding should be available in the initialisation code of the actor.

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