Stephan Ewen created FLINK-2788:
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Summary: Add type hint with TypeExtactor call on Hint Type
Key: FLINK-2788
URL: https://issues.apache.org/jira/browse/FLINK-2788
Project: Flink
Issue Type: Improvement
Components: Core
Affects Versions: 0.10
Reporter: Stephan Ewen
Fix For: 0.10
As per discussion with [~aljoscha]
A very good and type safe way to supply type hints would be the following:
Define a hint class that takes a generic parameter.
{code}
public abstract class TypeHint<T> {}
{code}
The hints would have the following method:
{code}
public DataSet<T> returns(TypeHint<T> hint);
{code}
It would be used like this:
{code}
DataSet<Sting> data = ...;
data
.flatMap( (String str, Collector<Integer> out) -> out.collect(str.length()) )
.returns( new TypeHint<Integer>() {})
{code}
This would create an inline subclass of the hint, from which the type could be
extracted. The generics would ensure that it is typesafe.
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