Get contract return value

How do I get the return value when calling a smart contract method? I use concordium_rust_sdk and client.send_block_item() but I do not understand how to retrieve the data that I am returning from my smart contract.

The return value is not possible to retrieve from the transaction.

You can get the return value if you invoke_instance instead, which executes the operation and returns the result, rather than committing a transaction. This is typically what you want for view functions.

Is that your use-case?

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Ha, just now I found it out myself. Ok, thanks, then I am on the right track.


Hey there, some clarification is needed on this.

Suppose I have a method “update” to a contract that changes state. I want to get the return value of that call. When I now invoke the contract, using the block that I get from the wait_until_finalized function, the state is already changed. Therefore, I cannot use the same contract method “update”. I must rather define a separate view method for getting the return value. Is that right?

Could I alternatively use an earlier block and use the “update” method?

You could use the parent block of the block your transaction ends up in.

But a more common thing would be to have a separate “view” function for viewing your state, and you use that one after the call if you need to view the state.

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