Is it possible to override a rails engine model association in a decorator? -

i'm using rails engine defines class following relation:

module blogit   class post < activerecord::base      ...      belongs_to :blogger, :polymorphic => true     ...  end 

i'm trying override association in decorator file. namely, not want association exist if possible.

in decorator file, i'm using class_eval extend class definition.

blogit::post.class_eval   ... end 

but can't seem override or destroy relation. know how this?