Promise vs Future

[Roman Novikov]

Why promise was introduced in 3.8? It seems duplicate functionality with futures.

[Julien Viet]

Hi,

in Vert.x 4 we use the promise/future and the Future interface removes the completion methods on it, so only Promise can be completed.

So a method returning a future creates Promise, keep a reference on the Promise to complete it and returns the Future from the method, e.g

default Future<Void> sendFile(String filename, long offset, long length) {
  Promise<Void> promise = Promise.promise();
  sendFile(filename, offset, length, promise);
  return promise.future();
}

In 3.x the future can still be completed, to avoid breaking but it is deprecated.

Julien

On 18 Oct 2019, at 17:41, Roman Novikov <myst...@gmail.com> wrote:

Why promise was introduced in 3.8? It seems duplicate functionality with futures.

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[Roman Novikov]

Hi Julien,

Now it's absolutely clear for me, thanks a lot!

On Saturday, October 19, 2019 at 4:28:13 PM UTC+3, Julien Viet wrote:

Hi,

in Vert.x 4 we use the promise/future and the Future interface removes the completion methods on it, so only Promise can be completed.

So a method returning a future creates Promise, keep a reference on the Promise to complete it and returns the Future from the method, e.g

default Future<Void> sendFile(String filename, long offset, long length) {
  Promise<Void> promise = Promise.promise();
  sendFile(filename, offset, length, promise);
  return promise.future();
}

In 3.x the future can still be completed, to avoid breaking but it is deprecated.

Julien

On 18 Oct 2019, at 17:41, Roman Novikov <myst...@gmail.com> wrote:

Why promise was introduced in 3.8? It seems duplicate functionality with futures.

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