Reply

The reply endpoint is another special one.

It relates to CosmWasm's actor model which dictates how you call other contracts and interact with them.

💡

If you are not familiar with the actor model, you can find out more about it on its own page.

This endpoint gets invoked when you receive a response to a message you sent out over the chain. The reply parameter then allows you to inspect and work with the response that was produced.

Request a reply

To request a reply, you need to use the reply_on field in the message you send and set it to one of the following values:

ReplyOn::Always
ReplyOn::Error
ReplyOn::Success

💡

The reply_on value has an impact on when a transaction is cancelled. For more info, check the page about transactions.

contract.rs

const CONTRACT_ADDR: &str = "other_contract";
const SUBMSG_ID: u64 = 1; // This is a unique identifier so we can associate a reply with a specific submessage. It can be any numeric value.
 
#[cfg_attr(not(feature = "library"), entry_point)]
pub fn reply(deps: DepsMut, env: Env, msg: cosmwasm_std::Reply) -> StdResult<Response> {
    if msg.id != SUBMSG_ID {
        return Err(StdError::generic_err("Invalid submsg id"));
    }
 
    // We received a message! From the contract we invoked earlier.
 
    Ok(Response::default())
}
 
#[cfg_attr(not(feature = "library"), entry_point)]
pub fn execute(deps: DepsMut, env: Env, msg: ExecuteMsg) -> StdResult<Response> {
    let msg = WasmMsg::Execute {
        contract_addr: CONTRACT_ADDR.into(),
        msg: to_json_binary(&OtherContractMsg::DoSomething {}).unwrap(),
        funds: vec![],
    };
 
    let submsg = SubMsg::reply_always(msg, SUBMSG_ID);
    Ok(Response::new().add_submessage(submsg))
}

Definition

contract.rs

#[cfg_attr(not(feature = "library"), entry_point)]
pub fn reply(deps: DepsMut, env: Env, msg: cosmwasm_std::Reply) -> StdResult<Response> {
    Ok(Response::default())
}

Sudo Actor Model