Events

CosmWasm can emit Cosmos Events. These events are stored in the block execution result as metadata, allowing the contract to attach metadata to what exactly happened during execution.

tip

Some important details about the keys:

• Whitespaces will be trimmed (i.e. removed from the beginning and end).
• Empty keys (that include keys only consisting of whitespaces) are not allowed.
• Keys can not start with an underscore '_', such keys are reserved for wasmd.

By default, CosmWasm emits the wasm event to which you can add attributes like so:

wasm_event.rs

let response: Response<Empty> = Response::new()
    .add_attribute("custom_attribute", "value");

Custom events

As mentioned above, CosmWasm only emits the event wasm by default. If you want to emit other events, such as domain-specific events like user_added, you can construct a fully custom event and attach it to the response.

tip

Note that those custom events will be prefixed with 'wasm-' by the runtime.

custom_event.rs

let event = Event::new("custom_event")
    .add_attribute("custom_attribute", "value");

let response: Response<Empty> = Response::new()
    .add_event(event);