Query

In the previous section we talked about the execute entrypoint. The query entrypoint is actually pretty similar to its sibling execute, but with one key difference: the storage is only accessible immutably. This means you can only read from the storage but not write to it.

Properly defining a message

When defining a message for queries, you always return some value. To properly document these return values, you'll want to define them in your schema.

This is where the cosmwasm_schema::QueryResponses derive macro comes in.

contract.rs

#[cw_serde]
struct GreetResponse {
  message: String,
}

#[cw_serde]
struct GoodbyeResponse {
  message: String,
}

#[cw_serde]
#[derive(QueryResponses)]
enum CustomQueryMsg {
  #[returns(GreetResponse)]
  Greet,
  #[returns(GoodbyeResponse)]
  Goodbye,
}

The macro then defines the required code to document the responses in your code properly, so you can easily generate, for example, TypeScript types for your contract clients.

Definition

contract.rs

#[cfg_attr(not(feature = "library"), entry_point)]
pub fn query(
    deps: Deps,
    env: Env,
    msg: QueryMsg,
) -> StdResult<QueryResponse> {
  // TODO: Prepare the response here.
  Ok(QueryResponse::default())
}