將模型中的方法轉換爲作用域：Rails3

我有兩個方法在我的模型項目中定義了正確工作。將模型中的方法轉換爲作用域：Rails3

1. def completed(user) 
     Project.find_by_sql(["Select p.id from bids b LEFT JOIN tasks t ON b.task_id=t.id LEFT JOIN projects p ON p.id = t.project_id where(b.bidder_id=? and b.status=? and p.status=?) group by p.id", user.id, 'ACCEPTED', 'COMPLETE']).count 
    end 

2. def current(user) 
     Project.find_by_sql(["Select p.id from bids b LEFT JOIN tasks t ON b.task_id=t.id LEFT JOIN projects p ON p.id = t.project_id where(b.bidder_id=? and b.status=? and p.status in ('LAUNCHED', 'CONFIRM', 'STAFFED', 'OVERDUE')) group by p.id", user.id, 'ACCEPTED']).count 
    end

當我將這些兩成範圍在項目模型

1. `scope :completed, proc{|user| joins("LEFT JOIN tasks t ON t.project_id=projects.id LEFT JOIN bids b ON b.task_id=t.id where(b.bidder_id='#{user.id}' and b.status='ACCEPTED' and p.status='#{COMPLETE_STATUS}')").count("DISTINCT p.id")}` 

2. `scope :current, proc{|user| joins("LEFT JOIN tasks t ON t.project_id=projects.id LEFT JOIN bids b ON b.task_id=t.id where(b.bidder_id='#{user.id}' and b.status='ACCEPTED' and p.status IN ('#{LAUNCHED_STATUS}', '#{CONFIRM_STATUS}', '#{STAFFED_STATUS}', '#{OVERDUE_STATUS}')) group by p.id").count("DISTINCT p.id")}`

我得到的錯誤爲：ActionView::Template::Error (PG::Error: ERROR: missing FROM-clause entry for table "p"

請給我建議，怎麼正確地寫這兩個範圍的陳述。謝謝。

來源

2013-01-07 Rakesh Jha

我不認爲範圍是更好的解決方案，導致一個計數，因爲使用範圍是爲了有一個過濾的對象列表。

無論如何，你的錯誤似乎來自你嘗試調用一個名爲「p」的表。「p」不存在，因爲這是您的方法中沒有在範圍中聲明的別名。

要解決這個問題，您只需要將「p」替換爲「projects」即可。

scope :completed, proc{|user| joins("LEFT JOIN tasks t ON t.project_id=projects.id LEFT JOIN bids b ON b.task_id=t.id where(b.bidder_id='#{user.id}' and b.status='ACCEPTED' and projects.status='#{COMPLETE_STATUS}')").count("DISTINCT projects.id")} 
scope :current, proc{|user| joins("LEFT JOIN tasks t ON t.project_id=projects.id LEFT JOIN bids b ON b.task_id=t.id where(b.bidder_id='#{user.id}' and b.status='ACCEPTED' and projects.status IN ('#{LAUNCHED_STATUS}', '#{CONFIRM_STATUS}', '#{STAFFED_STATUS}', '#{OVERDUE_STATUS}')) group by projects.id").count("DISTINCT projects.id")}

我希望這幫助

來源

2013-01-07 13:00:36

將模型中的方法轉換爲作用域：Rails3

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