Adding futures in for {} vs adding them outside of the for {}

Developer Corner
1

Hi,

I’ve been looking at go-samples and I’ve noticed that most of the loop defines futures, the selectors, and timers inside the main for {} is there a specific reason it’s not defined outside of the for {} and just selector.Select(ctx) is called?

For example:

In the await-signals sample:

func (a *AwaitSignals) Listen(ctx workflow.Context) {
	log := workflow.GetLogger(ctx)
	for {
		selector := workflow.NewSelector(ctx)
		selector.AddReceive(workflow.GetSignalChannel(ctx, "Signal1"), func(c workflow.ReceiveChannel, more bool) {
			c.Receive(ctx, nil)
			a.Signal1Received = true
			log.Info("Signal1 Received")
		})
		selector.AddReceive(workflow.GetSignalChannel(ctx, "Signal2"), func(c workflow.ReceiveChannel, more bool) {
			c.Receive(ctx, nil)
			a.Signal2Received = true
			log.Info("Signal2 Received")
		})
		selector.AddReceive(workflow.GetSignalChannel(ctx, "Signal3"), func(c workflow.ReceiveChannel, more bool) {
			c.Receive(ctx, nil)
			a.Signal3Received = true
			log.Info("Signal3 Received")
		})
		selector.Select(ctx)
		if a.FirstSignalTime.IsZero() {
			a.FirstSignalTime = workflow.Now(ctx)
		}
	}
}

Could this not be written as:

func (a *AwaitSignals) Listen(ctx workflow.Context) {
	log := workflow.GetLogger(ctx)
		selector := workflow.NewSelector(ctx)
		selector.AddReceive(workflow.GetSignalChannel(ctx, "Signal1"), func(c workflow.ReceiveChannel, more bool) {
			c.Receive(ctx, nil)
			a.Signal1Received = true
			log.Info("Signal1 Received")
		})
		selector.AddReceive(workflow.GetSignalChannel(ctx, "Signal2"), func(c workflow.ReceiveChannel, more bool) {
			c.Receive(ctx, nil)
			a.Signal2Received = true
			log.Info("Signal2 Received")
		})
		selector.AddReceive(workflow.GetSignalChannel(ctx, "Signal3"), func(c workflow.ReceiveChannel, more bool) {
			c.Receive(ctx, nil)
			a.Signal3Received = true
			log.Info("Signal3 Received")
		})
	for {

		selector.Select(ctx)
		if a.FirstSignalTime.IsZero() {
			a.FirstSignalTime = workflow.Now(ctx)
		}
	}
}

So my question is what absolutely has to go into the for {} or is there not even a difference?

2

I prefer the latter approach if there is no need to add new Futures or Channels to the Selector after the first Select is called.