Matteo Mortari created DROOLS-1245: -------------------------------------- Summary: Document limitation of (legacy) Accumulate CE Alternate Syntax: single function with return type Key: DROOLS-1245 URL: https://issues.jboss.org/browse/DROOLS-1245 Project: Drools Issue Type: Enhancement Components: docs Affects Versions: 6.4.0.Final Reporter: Matteo Mortari Assignee: Matteo Mortari Document limitations and common pitfalls: h2. from+accumulate does not iterate This does NOT iterate over the elements of the accumulate function: {code:java} rule R when $theFrom : Object() from accumulate(MyPerson( $val : name ); collectList( $val ) ) then list.add($theFrom); end {code} and in fact the binded $theFrom : Object() is the List returned by the collect list. While normally the "from" iterates over the element of list/iterable collections. {code:java} rule R1 when $list : List( ) $s : Integer() from $list then out.add($s); end {code} h2. limited scope of compile-time checks Compile-time checks are performed for Accumulate Functions returning a single result. Compile-time checks are NOT performed for iterable Accumulate Functions, the case when the accumulate function returns a collection. With ref to DROOLS-1243. For instance this fails at compilation: {code:java} rule R when $theFrom : BigDecimal() from accumulate(MyPerson( $val : age ); sum( $val ) ) then list.add($theFrom); end {code} but the following does passes compilation: {code:java} rule R when $theFrom : String() from accumulate(MyPerson( $val : name ); collectList( $val ) ) then list.add($theFrom); end {code} only to fail later at runtime with CCE: {code:java} Caused by: java.lang.ClassCastException: java.util.Collections$UnmodifiableRandomAccessList cannot be cast to java.lang.String {code} -- This message was sent by Atlassian JIRA (v6.4.11#64026)