有條件似乎去評估

Question

我有一個在Rails 4項目中設置像這樣的幾個模型。

student.rb

class Student < ActiveRecord::Base 
    has_many :contracts 

    def balance 
    unpaid_contracts.sum(&:sum_total) 
    end 

private 

    def unpaid_contracts 
    unpaid_contracts = [] 
    contracts.each do |c| 
     unpaid_contracts << c if c.unpaid? # This is the problem 
    end 
    end 

end 

contract.rb

class Contract < ActiveRecord::Base 

    has_many :invoices, dependent: :destroy 
    belongs_to :student 

    def unpaid? 
    return true if invoices.blank? 
    invoices.each do |i| 
     return true if i.current_status != "paid" && i.current_status != "rescinded" 
    end 
    end 
end 

無論我做什麼所有的合同被添加到unpaid_contracts。在db中根本沒有發票，所以我會假設unpaid?應該總是評估爲真，對不對？

事實上，即使我將條件更改爲unpaid_contracts << c if false問題仍然存在。

Answer 1

注意你的返回值：

def unpaid_contracts 
    unpaid_contracts = [] 
    contracts.each do |c| 
     unpaid_contracts << c if c.unpaid? # This is the problem 
    end 
    end 

你返回contracts.each，這是說所有合同，不unpaid_contracts。

這將修復它...

def unpaid_contracts 
    unpaid_contracts = [] 
    contracts.each do |c| 
     unpaid_contracts << c if c.unpaid? # This is the problem 
    end 
    unpaid_contracts 
    end 

但是，這是更好的：

def unpaid_contracts 
    contracts.select(&:unpaid?) 
    end 

Answer 2

你可以試試下面的

1. 私有方法只有你當不打算使用Class或Class的一個實例，所以試着把它拿出來。

2. 編碼它的稍微更合適的方法：

   def unpaid_contracts 
       contracts.select { |contract| contract.invoices.count == 0} 
   end 
   

3. 正如@meagar提到的，你是不是返回正確的變量。