如何將find_by_sql語句翻譯成named_scope？

Question

如何將以下內容轉換爲named_scope？

def self.commentors(cutoff=0) 
    return User.find_by_sql("select users.*, count(*) as total_comments from users, comments 
     where (users.id = comments.user_id) and (comments.public_comment = 1) and (comments.aasm_state = 'posted') and (comments.talkboard_user_id is null) 
     group by users.id having total_comments > #{cutoff} order by total_comments desc") 
    end 

這就是我現在所擁有的，但它似乎並沒有工作：

named_scope :commentors, lambda { |count=0| 
    { :select => "users.*, count(*) as total_comments", 
     :joins => :comments, 
     :conditions => { :comments => { :public_comment => 1, :aasm_state => 'posted', :talkboard_user_id => nil} }, 
     :group => "users.id", 
     :having => "total_comments > #{count.to_i}", 
     :order => "total_comments desc" 
    } 
    } 

Ulimately，這是什麼工作;

named_scope :commentors, lambda { |*args| 
     { :select => 'users.*, count(*) as total_comments', 
     :joins => :comments, 
     :conditions => { :comments => { :public_comment => 1, :aasm_state => 'posted', :talkboard_user_id => nil} }, 
     :group => 'users.id', 
     :having => ['total_comments > ?', args.first || 0], 
     :order => 'total_comments desc' } 
     } 

Answer 1

你的問題是因爲你從users, comments替代選擇與一個內部聯接與comments。要正確翻譯SQL到named_scope，使用此：

named_scope :commentors, lambda { |cutoff| 
    { :select => 'users.*, count(*) as total_comments', 
     :conditions => { :comments => { :public_comment => 1, :aasm_state => 'posted', :talkboard_user_id => nil } }, 
     :from => 'users, comments', 
     :group => 'users.id', 
     :having => ['total_comments > ?', cutoff], 
     :order => 'total_comments desc' } } 

而且你不能有拉姆達參數的默認值，所以你不能使用|cutoff = 0|。