Dart流中listen和forEach有什么区别？

Question

If I have Stream in Dart, I can use both listen and forEach , but I don't understand the difference.

So for example consider this code:

final process = await Process.start('pub', ['serve']);
process.stdout.map((l) => UTF8.decode(l)).forEach(print);

I could also have written:

process.stdout.map((l) => UTF8.decode(l)).listen(print);

Is there any difference?

Answer 1

The forEach function on a Stream will stop at the first error, and it won't give you a StreamSubscription to control how you listen on a stream. Using forEach is great if that's what you want - it tells you when it's done (the returned Future ) and all you have to do is handle the events. If you need more control, you can use the listen call which is how forEach is implemented.

It's like the difference between Iterable.forEach and Iterable.iterator - the former just calls a callback for each element, the other gives you a way to control the iteration.