SelectBuilder<R> class

Builder for composing async selections with type-safe operations.

Provides a fluent DSL for racing multiple async operations. Each operation type has specialized methods with automatic resource cleanup and cancellation.

Available Operations

Channel Operations:

• onRecv - Wait for any channel message (Success/Failure)
• onRecvValue - Wait only for successful channel messages
• onRecvError - Wait only for channel errors

Future Operations:

• onFuture - Race a Future with automatic cancellation
• onFutureValue - Race a Future, ignore errors
• onFutureError - Race a Future, only handle errors

Stream Operations:

• onStream - Wait for next stream event
• onStreamDone - Wait for stream completion

Timer Operations:

• onTick - Wait for timer tick
• onDelay - Add fixed delay branch
• onTimeout - Add timeout to the entire selection

Example - Multi-source data processing:

final processor = DataProcessor();

while (processor.isRunning) {
  final action = await XSelect.run<ProcessorAction>((s) => s
    // High-priority user commands
    ..onRecvValue(userCommands, (cmd) => ProcessorAction.userCommand(cmd))

    // Background data processing
    ..onStream(dataStream, (data) => ProcessorAction.processData(data))

    // Periodic maintenance
    ..onTick(Duration(days: 5), () => ProcessorAction.maintenance())

    // API health checks
    ..onFuture(healthCheck(), (status) => ProcessorAction.healthUpdate(status))

    // Graceful shutdown on idle
    ..onTimeout(Duration(minutes: 10), () => ProcessorAction.shutdown())
  );

  await processor.handleAction(action);
}