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Listening to Metamask events with Ethers in your Angular app
When you build your Angular application that connects to various blockchain accounts via MetaMask, it is essential to stay informed about events that occur in the context of your Ethereum-based services. In this article, we will explore how to set up listening to Metamask events using Ethers and Angular.
What are Metamask events?
Metamask events are notifications that can be sent or received by the MetaMask platform, indicating various state changes on your Ethereum account. These events can include things like:
- New accounts created
- Wallet balances updated
- Transaction events (e.g., receiving a transaction)
- Account ownership changes
Setting up Ethers Provider and Signer
To listen to Metamask events in your Angular app, you will first need to obtain an Ethers Provider instance. This will allow you to interact with the MetaMask API and send and receive events.
import { Component, OnInit } from '@angular/core';
import * as ethers from 'ethers';
@Component({
selector: 'app-example',
template: '
Example component.
'})
export class ExampleComponent implements OnInit {
myProvider: ethers.providers.Provider;
constructor() { }
ngOnInit(): void {
this.myProvider = new ethers.providers.Web3Provider(window.ethereum);
}
}
In the above code, we are creating a Web3 provider instance using the ethers package. You can get a Web3Provider instance by logging into your MetaMask account and then accessing the provider instance.
Listening to events
To listen to metamask events, you will need to subscribe to specific event types using the ethers subscription API.
import { Subscription } from 'rxjs';
const subscription: Subscription = this.myProvider.eventSubscriptions.subscribe((event) => {
console.log(Event received: ${event.name});
});
In the above code, we are creating a subscription that listens to events. We can specify the event types by passing them as an argument to the subscribe method.
Angular Service
To simplify managing subscriptions and listening to events in your Angular app, you can create a service.
import { Injectable } from '@angular/core';
import { EventSubscription } from './event-subscription';
@Injectable({
providedIn: 'root'
})
export class MetamaskService {
private subscription: Subscription;
constructor() { }
connectAccount(account: string): void {
this.subscription = this.myProvider.eventSubscriptions.subscribe((event) => {
console.log(Event received: ${event.name});
});
// Disconnect when account is closed
window.ethereum.onDisconnect(() => {
this.subscription.unsubscribe();
});
}
}
In the code above, we have created a MetamaskService class that manages subscriptions and listens to events. We can use instances of this service to connect to your MetaMask account.
Putting it all together
To listen to metamask events in your Angular app, you will need to:
- Create an instance of the ethers provider.
- Subscribe to specific types of events using the
subscribemethod.
- Use a service to manage subscriptions and manage event listeners.
Here is an updated example that demonstrates how to use these concepts:
“`typescript
import { Component, OnInit } from ‘@angular/core’;
import * as ethers from ‘ethers’;
@Component({
selector: ‘app-example’,
template: ‘
Example component.
‘
})
export class ExampleComponent implements OnInit {
myProvider: ethers.providers.Web3Provider;
subscription: Subscription;
constructor() { }
ngOnInit(): void {
this.myProvider = new ethers.providers.Web3Provider(window.
