This is what's in the unit test "test_ExtLegacy.drl":
declare BetterLegacy extends LegacyBean
    // novel field
    oneMoreField : String = "Hello"

    // inherited fields redeclared to set initial value
    doubleField : Double    = 3.3                @position(1) // tag inherited field, will be 1st field
    strField : String = "XX"
    intField : int = 245
    prop : boolean = true
    // objField is not redeclared
end

and this one "test_Extends.drl"
declare Person
    age : int     = 99          @position(2)
    name : String = "john doe" @key    @position(1)
end

declare Student extends Person
    school : String @key   @position(3)
end

declare LongTermStudent extends Student
    years : int @key @position(5)
    course : String @position(4)
end

On 28/05/2011 18:22, Wolfgang Laun wrote:

It doesn't work:

   declare Customer extends Person

is declined with

   Cannot extend supertype 'date.cust.Person' (not a declared type)

-W

2011/5/28 Edson Tirelli <ed.tirelli@gmail.com>

   Wolfgang,

   I think Davide's implementation supports extending existing java classes... did you tried? What is not possible is to implement interfaces, since you can't define methods in the declare statement.

   Edson

2011/5/28 Wolfgang Laun <wolfgang.laun@gmail.com>

There is, since 5.2.0, the option of extending a class declared in DRL:

declare A
   i : int
end

declare B extends A
...
end

Any class origninating from Java code cannot be extended in DRL.

-W

On 28 May 2011 10:56, Tomas Olsson <tol@sics.se> wrote:

Hi,
I have tried to look this up but cannot find any clear answer on the web.
Does drools support extension of existing classes for new type declarations?
That would be very nice if this would be possible.

/Tomas
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--
Edson Tirelli
JBoss Drools Core Development
JBoss by Red Hat @ www.jboss.com

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