Hi all,
Right now when you want to use MapElements<A, B> (and friends) you have two
options:
1. Use a SimpleFunction Java 7 style
MapElements.via(SimpleFunction<A, B>() {
@Override
public B return apply(A input) {
return ...expr...;
}
}
and the type descriptors are automatically inferred
2. Use a lambda and withOutputType
MapElements.via((A input) -> ...expr...)
.withOutputType(new TypeDescriptor<B>(){})
MapElements.via((A input) -> ...expr...)
.withOutputType(TypeDescriotors.bs())
and you might have a handy helper in TypeDescriptors (note the plural) or
you might have to create your own, which is a weird pattern if you haven't
seen it before. Both shown above.
[PROPOSAL] Here is a neat trick for getting type information like in #1 but
with a lambda like #2 and a bit less verbosity:
MapElements.via(new SimpleFunction<A, B>((A input) -> ...expr...) {})
I think we can add this. I lean towards this just being a third option, but
could be easily swayed to drop #2.
This is https://github.com/apache/beam/pull/1855 where you can see some
unit tests demonstrating it more, and take a look at what it means for
error checking, etc. It is backwards-compatible but still a change to a
core API so deserves a thread on list.
Thoughts?
Kenn
