FlinkCEP 1.3 scala, cannot apply select function

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FlinkCEP 1.3 scala, cannot apply select function

Sonex
Hello I have created a simple pattern with FlinkCEP 1.3 as well as a simple pattern select function. My simple function is as follows:

def myFunction(pattern: Map[String,Iterable[MyEventType]]): MyEventType = {
    val startEvent = pattern.get("first").get.head
    val endEvent = pattern.get("second").get.head
    // dummy functionality for illustrating purposes
    endEvent
}

When I apply the function above to a pattern in the following way:

CEP.pattern(myKeyedStream,myDummyPattern).select(myFunction(_)) it gives the following error:

Cannot resolve reference myFunction with such signature.

Type mismatch, expected: scala.Predef.Map[scala.Predef.String,scala.Iterable[MyEventType]], actual: scala.collection.Map[scala.Predef.String,scala.Iterable[MyEventType]]

What is the reason of this behavior?

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Re: FlinkCEP 1.3 scala, cannot apply select function

Dawid Wysakowicz
Hi,

Because of some optimizations between java <-> scala collections conversions, the type of Map used for select method is scala.collection.Map instead of Predef.Map imported by default.

Try importing:

import scala.collection.Map

or use fully qualified name in function definition: 

def myFunction(pattern: scala.collection.Map[String,Iterable[MyEventType]]): MyEventType = {
    val startEvent = pattern.get("first").get.head
    val endEvent = pattern.get("second").get.head
    // dummy functionality for illustrating purposes
    endEvent
}

Z pozdrowieniami! / Cheers!


Dawid Wysakowicz

Data/Software Engineer

Skype: dawid_wys | Twitter: @OneMoreCoder


2017-06-19 9:35 GMT+02:00 Sonex <[hidden email]>:
Hello I have created a simple pattern with FlinkCEP 1.3 as well as a simple
pattern select function. My simple function is as follows:

def myFunction(pattern: Map[String,Iterable[MyEventType]]): MyEventType = {
    val startEvent = pattern.get("first").get.head
    val endEvent = pattern.get("second").get.head
    // dummy functionality for illustrating purposes
    endEvent
}

When I apply the function above to a pattern in the following way:

CEP.pattern(myKeyedStream,myDummyPattern).select(myFunction(_)) it gives the
following error:

Cannot resolve reference myFunction with such signature.

Type mismatch, expected:
scala.Predef.Map[scala.Predef.String,scala.Iterable[MyEventType]], actual:
scala.collection.Map[scala.Predef.String,scala.Iterable[MyEventType]]

What is the reason of this behavior?





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Re: FlinkCEP 1.3 scala, cannot apply select function

Sonex
Thank you for your quick response. That worked and compiled but another error came up. On runtime it gives the following error:

java.lang.ClassCastException: MyEventType cannot be cast to scala.collection.IterableLike

The error is at line

val startEvent = pattern.get("first").get.head

of myFunction.
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