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Subject: Re: extending a class with an @Delegate
To: users@groovy.apache.org
References: <b5c2f018-323f-df2b-ce2f-c26bc0fae109@gmail.com>
From: Jochen Theodorou <blackdrag@gmx.org>
Message-ID: <f9e7dc0f-9e0a-d7d6-a350-4f8528005747@gmx.org>
Date: Thu, 23 Mar 2017 13:53:55 +0100
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On 23.03.2017 11:56, paul wrote:
> Suppose I have two Classes, one extending the other:
>
> class Person{ String name, int age}
> class Pupil extends Person {int grade}
>
> Now to manage several Persons in a List, and add some custom methods, I
> use the @Delegate like
>
> class Personlist{
>   @Delegate List<Person> persons
>
>   Personlist underAge(n){persons.findAll{it.age<=n} as Personlist}
> }
>
> Pupillist should have the same methods (since each pupil is a person):
>
> class Pupillist extends Personlist{
>   Pupillist inGrade(g){persons.findAll{it.grade==g} as Pupillist}
> }
>
> Now I want to chain several of these methods like this:
> def pl = [...] as Pupillist
> pl.underAge(12).inGrade(9)
>
> throws a MissingMethodException, because `pl.underAge` gets cast into a
> Personlist, which has no method `inGrade`.


How about not working with Delegate and instead use a category for the 
methods and just return a list?

bye Jochen