I wrote an action that has an optional parameter, as something like:

[[eosio::action]] void foo(..., const std::optional<name>& recipient);

Then in the generated .abi, it is represented as:

{"name": "recipient", "type": "name?"}

But I couldn't find a way to specify (or, not specify) the optional parameter for cleos. Itried without specifying the optional parameter, {..., "recipient": ""}, etc., all in vain.
What should I do to specify an optional action parameter for cleos?

1 Answer 1


If you want to specify the value for optional param, just pass value like normal type. For not specifying value, use null.

{..., "recipient": "eosio"} or {..., "recipient": null}

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