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https://issues.apache.org/jira/browse/FLINK-1458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14295010#comment-14295010
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Aljoscha Krettek commented on FLINK-1458:
-----------------------------------------
Yes, after the fix is merged it will indeed work.
If you later on add fields to SimpleClass, you have to make sure that they are
public or have getters/setters and that the class has a
zero-argument-constructor, like so:
{code}
class SimpleClass(var a: Double) extends SimpleTrait {
def this() = this(0.0)
def contains(x: String) = true
override def toString: String = "Simple Class " + a
}
{code}
> Interfaces and abstract classes are not valid types
> ---------------------------------------------------
>
> Key: FLINK-1458
> URL: https://issues.apache.org/jira/browse/FLINK-1458
> Project: Flink
> Issue Type: Bug
> Reporter: John Sandiford
>
> I don't know whether this is by design or is a bug, but I am having trouble
> working with DataSet and traits in scala which is a major limitation. A
> simple example is shown below.
> Compile time warning is 'Type Main.SimpleTrait has no fields that are visible
> from Scala Type analysis. Falling back to Java Type Analysis...'
> Run time error is 'Interfaces and abstract classes are not valid types:
> interface Main$SimpleTrait'
> Regards, John
> val env = ExecutionEnvironment.getExecutionEnvironment
> trait SimpleTrait {
> def contains(x: String): Boolean
> }
> class SimpleClass extends SimpleTrait {
> def contains(x: String) = true
> }
> val data: DataSet[Double] = env.fromElements(1.0, 2.0, 3.0, 4.0)
> def f(data: DataSet[Double]): DataSet[SimpleTrait] = {
> data.mapPartition(iterator => {
> Iterator(new SimpleClass)
> })
> }
> val g = f(data)
> g.print()
> env.execute("Simple example")
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