feat: Accessing the Event Stream Should Depend on scanner.start() Being Invoked #146
Description
The problem currently is that it is easy to forget to call scanner.start() before starting to read the event stream.
This could be addressed using a sort of typestate pattern (open for discussion, need your input @LeoPatOZ ):
scanner.start()returns some structScannerStartedTokenthat cannot be instantiated outside the cratescanner.subscribe(filter)returnsSubscription- stream can only be accessed by passing the
ScannerStartedTokenlike:subscription.stream(scanner_started_token) - this ensures that
scanner.start()must be called before streaming can start
Full example:
// init scanner as before
let mut scanner = EventScannerBuilder::sync().from_block(0).connect(provider);
let filter = EventFilter::new();
// create subscription
let subscription = scanner.subscribe(filter);
// because scanner wasn't started, client can't access stream events yet
// let mut stream = subscription.stream(!!!missing token - won't compile!!!);
// start scanner
// name `token` used for simplicity, exact name open for discussion
let token = scanner.start().await?;
// now we're sure scanner is started, we can access the stream
let mut stream = subscription.stream(&token);
while let Some(msg) = stream.next().await {
// ...
}