Dealing with ProcessorDefinition

In my org.apache.camel.scala.dsl.builder.RouteBuilder when I write

from ==> {
idempotentConsumer(uuid) repository db choice {
...

everything is OK, however when I want to write

from ==> {
if( idempotencyIsSet) {
idempotentConsumer(uuid) repository db

choice {
...

route is silently not started and not working...

My problem is not to know how to properly use scala DSL:(