[rules-users] Call class method from LHS of a rule

[Wolfgang Laun]

2010/1/4 Esteban Aliverti <esteban.aliverti at gmail.com>

> Using Wolfgang's inline eval epression, I get the following error: "Cannot
> use this in a static context" when compiling the rule. I changed
> "this" by "$c" and it works. I don't know why we are in a static context.
>
>
Strange. Most likely the compiler converts the inline eval to an eval CE,
where you can't have "this".
I have occasionally used s.th. like
   $foo : Foo( $bar : bar )
   Bar( this == $bar )
which goaded me into thinking that this.method() should work in an inline
eval.

Thanks for checking this, though!
-W

The rule that worked for me is:
>
> Rule "Rule1"
>  when
>    $c:Cheese(type == "chedar", eval($c.existsInShop ("shopName"))
>
>  then
>    System.out.println("Rule1 is fired");
> end
>
> I attached a working test case. Change $c to "*this" *in rule's condition
> and you will see the error I mentioned.
>
> Best,
>
> 2010/1/4 Wolfgang Laun <wolfgang.laun at gmail.com>
>
>> What you need is called "inline eval expression" (see the Drools Expert
>> manual),
>> or an eval conditional element. The first one might be written as:
>>
>> $c:Cheese(type == "chedar", eval( this.existsInShop("shopName") ) )
>>
>> -W
>>
>>
>>
>> On Mon, Jan 4, 2010 at 12:49 PM, orchid <maya.pollack at gmail.com> wrote:
>>
>>>
>>> Hi All,
>>>
>>> I'm trying to call a class method from the LHS of a rule in the following
>>> way:
>>>
>>> public class Cheese{
>>>  private string type;
>>>  //setters and getters
>>>  public boolean existsInShop(String shop){
>>>    ...
>>>    return true;
>>>  }
>>> }
>>>
>>> I would like to call the method "existsInShop" from a rule:
>>>
>>> Rule "Rule1"
>>>  when
>>>    $c:Cheese(type == "chedar", existsInShop "shopName")
>>>  then
>>>    System.out.println("Rule1 is fired");
>>> end
>>>
>>> I get the compilation error: "no viable alternative at input "shopName"
>>> in
>>> rule "Rule1" in pattern document". How can I call the method from the
>>> rule?
>>>
>>> Thanks in advance.
>>>
>>>
>>>
>>> --
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>>
>>
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>
>
> --
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
>
> Esteban Aliverti
>
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