Cancan state management and migration

nicolas-martin · November 9, 2021, 4:53pm

Hey all,

I’ve been looking at Cancan’s binary relational implementation and I was wondering how is state persisted between canister upgrades?

Currently main.go calls these 2 functions from states but afaik they’re use a base library that’s not implemented.

github.com

dfinity/cancan/blob/main/service/CanCan.mo#L46-L52

    
      
          /*public query*/ func getState() : async State.StateShared {
            State.share(state)
          };
          
          
/*public*/ func setState(st : State.StateShared) : async () {
            state := State.fromShared(st);
          };

github.com

dfinity/cancan/blob/main/backend/State.mo#L256-L262

    
      
          public func share(state : State) : StateShared {
            Prelude.nyi() // to do -- for testing / upgrades sub-story
          };
          
          
public func fromShared(share : StateShared) : State {
            Prelude.nyi() // to do -- for testing / upgrades sub-story
          };

I also had a look at matthew hammer’s implementation, which still has stable memory as an upcoming feature

github.com

matthewhammer/motoko-example-20210805/blob/main/src/State.mo

import Prelude "mo:base/Prelude";
import Text "mo:base/Text";
import Int "mo:base/Int";
import Trie "mo:base/Trie";
import TrieMap "mo:base/TrieMap";

// import non-base primitives
import Rel "Rel";
import RelObj "RelObj";
import SeqObj "SeqObj";

// types in separate file
import Types "Types";

/// Internal CanCan state.
module {

  // Our representation of (binary) relations.
  public type RelShared<X, Y> = Rel.RelShared<X, Y>;
  public type Rel<X, Y> = RelObj.RelObj<X, Y>;

This file has been truncated. show original

If the features from the standard library aren’t ready, is there a recommended way to do for now?

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Cancan state management and migration

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