A guide to events and logs in Ethereum Smart Contracts

 Events and logs in Ethereum play a vital role since they are responsible for communication between the user interface and smart contracts. Similar to callback response in traditional web development, Ethereum uses smart contracts for the emission of events and writes logs to address the same. Events and logs used in Ethereum has three main use cases,

• Smart contract return values for the front end

• Asynchronous triggers with data

• A cheaper form of storage

Let us get to know about each of them in detail.

Events and Logs in Ethereum - Use Cases

#1 Smart contract return values for the front end

The first use case is sending return values from the contracts to the user interface(front-end). The contract execution is simulated so that the return value can be obtained. This whole concept arose since transactions cannot return a value. This issue was taken care of with the advent of events.

#2 Asynchronous triggers with data

Asynchronous triggers with data are nothing but events. When the front end needs to be triggered by the smart contract, it eventually emits an event. The interface can take action to display anything on the front end by retrieving value while watching for events. Return values are a minimal use case compared to how events are used as triggers.

#3 A cheaper form of storage

Events can be used as a cheaper form of storage. In the Ethereum Virtual Machine (EVM), the events are termed logs. As discussed before, contracts trigger events and when the event is emitted, the logs are written in the blockchain, basically storing data. Logs contain less gas than contract storage. They are not accessible from smart contracts and the cost of storage is also low compared to contract storage. 

Indexed Parameters - Sending and Receiving

While transferring values through an event, up to three parameters can be indexed. The interface can watch for transfer for tokens that can be,

• Sent by a token address

• Received by a token address

• Sent by one address to a specific token address

Wrap Up

Thus events can be used for getting return values, used as the asynchronous trigger for data, and used to write logs, a cheaper form of data storage in the blockchain. To adopt these use cases while developing your smart contract, make sure you partner with the best-in-class smart contract app development company to achieve the same. Uberdoo is a renowned mobile app development company holding expertise in developing smart contracts using such efficient use cases and methods. Do you wish to know more about their services? Then you should probably contact their expert team soon and get in the crypto game with exemplary smart contract-supported apps!