Displaying Solidity Custom Errors on the Front-End
When developing complex decentralized applications (dApps), it is not uncommon to encounter custom errors that cannot be caught using traditional error handling mechanisms. In this article, we will explore how to display these custom errors on the front-end using the Ethereum web3.js library.
Why display custom errors?
Custom errors often occur due to unexpected logic in your contract or third-party integrations. By displaying them on the front-end, you can:
- Improve user experience
: Users will appreciate a clear indication that something has happened.
- Improve debugging tools: Developers can use these custom errors to more effectively identify and resolve issues.
Required Conditions
Before diving in, make sure you have:
- Basic understanding of Solidity and web3.js
- Contract deployed on the Ethereum blockchain
Viewing mapped errors using web3.js
In this example, we’ll use web3.js to provide custom errors for the front-end application. We’ll create an event emitter that will listen for CustomError events emitted by your contract.
First, install the web3.js and w3-logger libraries:
”attempt
npm install web3 w3-logger
Implementing the Agreement
" strength
pragmatic solidity 0.8.16;
Test Contract {
event CustomError(uint256 value);
public uint a;
public constructor() {
emit CustomError(10); // Example error code
}
pure extern function testFunction() return (bool) {
a = 5; // This should raise a custom error
return true; // Successful execution
}
}
Installing the Front End
`javascript
import * as w3 from "web3";
import { Events } from "w3-logger";
class FrontendApp {
constructor(w3Instance) {
this. w3 = w3Instance;
const eventEmitter = new Events();
eventEmitter. on("Custom error", (error value) => {
console. error(Custom error: ${errorValue});
// Handle custom error logic here
});
// Setup agreement
deployContract(w3Instance);
}
Async Deploy Contract (w3Instance) {
const contractAddress = "0x..."; // Replace with your contract address
const contractAbi = "..."; // Replace ABI with your contract
const web3 = new w3. Web3(w3Instance, contractAbi);
await web3. eth. deployContract(contractAddress);
}
}
Running the Counter ProgramTo run this frontend application, you will need to create a new Solidity contract and deploy it. Then import the FrontendApp class and call its constructor.
javascriptconst w3Instance = require("web3")("
const frontendApp = new FrontendApp(w3Instance);
Custom Error Handling
You can handle custom errors in your frontend application using a try-catch block:
javascript
try {
const result = await frontendApp.testFunction();
console.log(result);
} catch (error) {
console.error(Custom error: ${error.message});
}
“
By displaying custom errors in the interface, you can improve the user experience of your application and make it easier for developers to identify and resolve issues.
Conclusion
Displaying optional errors is a crucial step in building robust decentralized applications. By using web3.js and implementing a custom error handling system, you can improve the usability and debugging capabilities of your front-end application. This example shows how to deploy a contract on the Ethereum blockchain and display custom errors in the interface using web3.js.
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