Active Record - faire des jointures imbriquées avec conditions

Source SO

Try to change your where clause :

Publication  .joins( :publication_contributors => :contributor )
  .where( :publication_contributors => {:contributor_type => "Author"}, 
          :contributors             => {:name => params[:authors]} ) 

ActiveRecord api is not extremely consistent here: the arguments for where do not work exactly as those for joins. This is because the arguments for joins do not reflect the underlying SQL, whereas the arguments for where do.

where accepts an hash whose keys are table names, and values are hashes (that themselves have column names as keys). It just prevents ambiguity when targetting a column that has the same name in two tables.