Hey,
the TypeExtractor.getForClass() is only intended for primitive types, if
you want to extract all kinds of types you should use
TypeExtractor.createTypeInfo(Type t) (a class is also a type). However,
I think it would be better if your method takes TypeInformation as an
argument instead of a class, because otherwise the user has to extend
tuple in order to provide the tuple field types.
Regards,
Timo
On 08.11.2014 19:04, Vasiliki Kalavri wrote:
Hello again,
I tried out your suggestion and made a variation of the mapVertices method,
which takes the class of the new value as an argument.
In order to extract the type from the class, I use
the TypeExtractor.getForClass() method.
Is this what you had in mind?
When testing, this seems to work fine for basic types and for a custom
custom class I tried, but I get an error when trying to change the value
type to a Tuple. Do I have to deal with Tuples separately or is there a
better way to extract the type?
Thanks!
Cheers,
V.
On 31 October 2014 01:16, Vasiliki Kalavri <[email protected]>
wrote:
Hi Timo,
thank you for the explanation!
I guess I will try implementing ResultTypeQueryable then :)
Cheers,
Vasia.
On 30 October 2014 13:01, Timo Walther <[email protected]> wrote:
Hi Vasiliki,
your error is a very common problem we have together with types. The
problem is that Java does type erasure, which means that
return vertices.map(new ApplyMapperToVertex<K, VV>(mapper));
becomes
return vertices.map(new ApplyMapperToVertex(mapper));
Therefore we don't have the types. But since we have "implements
MapFunction<Tuple2<K, VV>, Tuple2<K, VV>>" the type extractor infers the
output through the input (which is always known).
The return type must be provided manually e.g. by implementing the
interface ResultTypeQueryable or by the a new API operator (see my last
mailing list mail).
Regards,
Timo
On 30.10.2014 11:59, Vasiliki Kalavri wrote:
Hi all,
one of the operations we want to implement for the flink graph api is
mapVertices, i.e. applying a mapper to the vertices of the graph.
The current implementation assumes that the vertex value type remains the
same:
https://github.com/project-flink/flink-graph/blob/master/
src/main/java/flink/graphs/Graph.java
.
However, we would like to be able to change the vertex value type. When
trying this out, we got this error:
Type of TypeVariable 'NV' in 'class flink.graphs.Graph$
ApplyMapperToVertex'
could not be determined. This is most likely a type erasure problem. The
type extraction currently supports types with generic variables only in
cases where all variables in the return type can be deduced from the
input
type(s).
How could we solve this and support changing the vertex value type?
Thank you!
Cheers,
Vasia.
