App Engine Jruby DataMapper列表屬性

Question

如何在Google AppEngine的Jruby上的DataMapper中使用list/array作爲屬性？

Answer 1

這會像has..and..belongs..to..many，無需連接表...

class Person 
    include DataMapper::Resource 
    property :id,   Serial 
    property :name,  String, :nullable => false 
    property :project_ids, List 
    timestamps :at 
    # project should be flagged as archived, not deleted 
    def projects 
    Project.all(:id => project_ids) 
    end 
end 

class Project 
    include DataMapper::Resource 
    property :id,   Serial 
    property :name,  String, :nullable => false 
    property :archived, Boolean, :default => false 
    # the join table is bolted onto the person model 
    def people 
    Person.all(:project_ids => id) 
    end 
end