Displaying Custom Solidity Errors in the UI
When building complex decentralized applications (DAPPS), it is not uncommon to encounter inherent errors that cannot be caught by traditional error handling mechanisms. In this article, we will explore how to display these custom errors in the UI using Ethereum’s Web3.js library.
Why Show Custom Errors?
Custom errors are often the result of unexpected logic in your contract or third-party integrations. By displaying them in the UI, you can:
- Improve the user experience
: Users will appreciate a clear indication that something is wrong.
- Improve debugging tools: Developers can use these custom errors to identify and resolve issues more effectively.
Assumptions
Before we begin, make sure you have:
- A basic understanding of solidity and web3.js
- A contract implemented on the Ethereum blockchain
Displaying custom errors using web3.js
In this example, we will use Web3.js to display custom errors in the Frontend application. We will create an event emitter that listens to the Customerror events emitted by your contract.
First, install the Web3.js and W3-Logger libraries:
`Just
NPM install Web3 W3-Logger
`
Implementing the contract
`Solidity
Pragma Solidity 0.8.16;
test contract {
event CustomError(value Uint256);
uint public a;
constructor () public {
emit UserError(10); // Example error code
}
function testFunction() extern net return (bool) {
A = 5; // This should raise its own error
return true; // Successful execution
}
}
`
Interface implementation
`JavaScript
import * as W3 from “Web3”;
import {events} from “W3-Logger”;
class frontendApp {
constructor (w3instance) {
this.w3 = w3instance;
const eventMitter = new Events();
eventEmitter.on (“customerror”, (errorValue) => {
Console.Error(Custom error: ${errorValue});
// Handle your own error logic here
});
// contract implementation
implementation (W3Instance);
}
async deploy(w3instance) {
Const ContractAddress = “0x …”; // Replace with contract address
Const ContractAbi = “…”; // Replace ABI contract
Const Web3 = new W3.Web3(W3Instance, ContractAbi);
expect web3.eth.DeployContract(ContractAddress);
}
}
`
Getting the interface started
To get this Frontend app up and running, you’ll need to create a new Solidity contract and implement it. Then import the “frontendApp” class and call its constructor.
`JavaScript
const w3instance = require(“web3”)(“
const frontendApp = new frontendApp(W3Instance);
`
Custom Error Handling
You can handle your own errors in your Frontend app using a Try-Catch block:
`JavaScript
try {
const result = expect frontendApp.Testfunction();
Console.log(result);
} catch (error) {
Console.Error(Custom Error: ${Error.Message});
}
`
By displaying custom errors on the UI, you can improve the user experience of your application and make it easier for developers to identify and resolve issues.
Conclusion
Handling your own errors is a necessary step in building robust decentralized applications. By using Web3.js and implementing your own error handling system, you can improve the usability and debuggability of your Frontend application. This example shows how to implement a contract on the Ethereum blockchain and display custom errors on the UI using web3.js.
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