2.10. Events#

Syntax#

EventDefinition = (* event_keyword: *) EVENT_KEYWORD
                  (* name: *) IDENTIFIER
                  (* parameters: *) EventParametersDeclaration
                  (* anonymous_keyword: *) ANONYMOUS_KEYWORD?
                  (* semicolon: *) SEMICOLON;

EventParametersDeclaration = (* open_paren: *) OPEN_PAREN
                             (* parameters: *) EventParameters
                             (* close_paren: *) CLOSE_PAREN;

EventParameters = ((* item: *) EventParameter ((* separator: *) COMMA (* item: *) EventParameter)*)?;

EventParameter = (* type_name: *) TypeName
                 (* indexed_keyword: *) INDEXED_KEYWORD?
                 (* name: *) IDENTIFIER?;

Event Definitions#

Events are convenient interfaces with the EVM logging facilities. They have to be defined inside a contract:

contract MyContract {
    // Defining an event
    event BidPlacedEvent(address bidder, uint amount);

    function bid() public payable {
        // Triggering an event
        emit BidPlacedEvent(msg.sender, msg.value);
    }
}