November 2018
Intermediate to advanced
528 pages
13h 21m
English
Content preview from Blockchain By Example
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Events
Events allow for the convenient use of the EVM logging facilities. They are an important concept in smart contracts, as any off-chain environment connected to Ethereum's JSON-RPC API can listen to these events and act accordingly.
In general, there are three main use cases for events and logs in DApps:
- To return values from a smart contract to a user interface
- To provide asynchronous triggers with indicative data that we can listen for in the frontend
- As a cheaper form of storage in the blockchain
When they are called, they cause their arguments to be stored in the transaction's log. An event is declared as using the event keyword, as follows: event CanceledEvent(string message, uint256 time);.
In the declaration, we determine the ...
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