How to map a Future (in Java)

[Stikkos]

Hello,

I am trying to map a Future as defined on http://doc.akka.io/docs/akka/2.1-M2/java/futures.html

Basically, I just want to 'cast' my Future<Object> to a Future<Response> using the following code:

import akka.dispatch.Future;

import akka.japi.Function;

import akka.pattern.Patterns;

final Future<Object> wrappedFuture = Patterns.ask(matchedHandler, message, handleCommandTimeout);

final Future<Response> responseFuture = wrappedFuture.map(new Function<Object,Response>() {

public Response apply(Object source) {

Response response = null;

if(source instanceof Response){

response = (Response) source;

}

return response; 

});

The problem is that this doesn't compile.

The method map(Function1<Object,A>) in the type Future<Object> is not applicable for the arguments (new Function<Object,Response>(){})

Any idea how I should use the Future.map function?

Thanks!

[√iktor Ҡlang]

Hi Stikkos,

From the link you posted:

1. Future<Integer> f2 = f1.map(new Mapper<String, Integer>() {
2. public Integer apply(String s) {
3. return s.length();
4. }
5. }, ec);

However, if you just want to make a typesafe cast, use "mapTo".

Cheers,

√

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[√iktor Ҡlang]

I also recommend upgrading from 2.1-M2 to 2.1.0-RC1 :-)

Cheers,

√

[Stikkos]

Thank you!

Could you give me a quick example of how to use the "mapTo" for a type-safe cast in Java or a link to the documentation for this method please?

[Stikkos]

I've found it ;-)

final Future<Response> responseFuture = wrappedFuture.mapTo(Util.manifest(Response.class));

[√iktor Ҡlang]

On Sun, Oct 28, 2012 at 4:07 PM, Stikkos <sti...@gmail.com> wrote:

I've found it ;-)

final Future<Response> responseFuture = wrappedFuture.mapTo(Util.manifest(Response.class));

Great, (in 2.1.0-RC1 it's Util.classTag(Response.class)) You can use a static import to make it look nicer:

import static akka.japi.Util.manifest;

final Future<Response> responseFuture = wrappedFuture.mapTo(manifest(Response.class));

Happy hAkking!

√