Deserialize ContractEvents (concordium/web-sdk:^8.1.0)

Node
1

Hello!

I have a node app with the dependency: “@concordium/web-sdk”: “^8.1.0”

Some other part of the program is sending a minting process of a CIS2 token, and after it is sent to the blockchain, it waits for the transactionHash to be finalized using this code:

await concordiumNodeClient.getBlockItemStatus(transactionHash);

Once the tx is correctly finalized, it tries to deserialize the outcome of the transaction with the intention of finding out the token Ids that are minted.

This is an example of the events raised from the contract:

// Mint the token in the state.

let token_id = state.mint(&params.token, &params.owner, builder);

// Event for minted token.

logger.log(&Cis2Event::Mint(MintEvent {
    token_id,
    amount: concordium_cis2::TokenAmountU64(1),
    owner: params.owner,
}))?;

// Metadata URL for the token.

logger.log(&Cis2Event::TokenMetadata::<_, ContractTokenAmount>(
    TokenMetadataEvent {
        token_id,
        metadata_url: params.token.metadata_url.first().unwrap().clone(),
    },
))?;

As you can see, two events are raised everytime a token is minted… the MintEvent and the TokenMetadataEvent.

That is actually what i can see in the getBlockItemStatus method response:

{
   ...
   "events":[
      "fe011101001ccebf8fd2005ba1779c7568936901ae2d438be75711f45fcbc9104eb5c8ddc7",
      "fb0111670068747470733a2f2f35746172732d637269636b65742d6173736574732e73332e616d617a6f6e6177732e636f6d2f637573746f6d2d6d657461646174612f37323235343735362d336466302d343465382d623131622d6666383435373035363663652e6a736f6e00"
   ],
   ...
}

But now I don’t seem to find a nice way to unmarshall those two events in a smart way… so I can get 2 JSONS like this:

[ 
   {
        token_id: 1,
        amount: 1,
        owner: "blablabla"
    },
   {
        token_id: 1,
        metadata_url: "https://metadata.json"
    }
]

Any thoughts? Thanks in advance!!!

2

It looks like these are CIS2 events, so you should be able to use deserializeCIS2EventsFromSummary to deserialize them into a usable form.

3

Hello,

I finally found the solution,

  1. Having these two events:
[
  "fe011101001ccebf8fd2005ba1779c7568936901ae2d438be75711f45fcbc9104eb5c8ddc7",
  "fb0111670068747470733a2f2f35746172732d637269636b65742d6173736574732e73332e616d617a6f6e6177732e636f6d2f637573746f6d2d6d657461646174612f37323235343735362d336466302d343465382d623131622d6666383435373035363663652e6a736f6e00"
]
  1. Importing the class “ContractEvent” from @concordium/web-sdk and executing the parseWithSchemaTypeBase64 method, passing the hex of the event mentioned above and the event hash retrieved from the schema.json after compiling the contract.
ContractEvent.parseWithSchemaTypeBase64(eventHex, eventHash);
  1. Probably deserializeCIS2EventsFromSummary would have done the trick as well, but this way makes more sense if new events are raised in the contract that are not standard :slight_smile:

Thanks for the help!!!