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I'm trying to get a current balance per transaction, a simple summation (Credit's up to record - Debits up to record) on an ordered list.

The challenge is that transactions are often entered out of order, and the transaction logs are sorted by a "Dated" field (showing the date it should have been entered) and by "credits" first (so that it shows payments before bills on the same day).

The association is sorted:

has_many :rent_logs, :order => [:dated, "credit desc"]

Data is presented simular to the following

[ID] Dated  Label   Credit  Debit   Balance [Needs excel summation look]
[20] 1/1/13 payment 600.0          -30 *    [Should be: 600 ]
[1 ] 1/1/13 Rent Due        630.0  -30      [Ok here  : -30 ]
[2 ] 2/1/13 Rent Due        630.0  -660     [Ok here  : -660]
[28] 2/6/13 Late Fee        50.0   -710     [Ok here  : -710]
[7 ] 3/1/13 payment 1200.0         -140*    [Should be: 490 ]
[3 ] 3/1/13 Rent Due        630.0  -140     [Ok here  : -140]

* Indicates massive fail on running balance

I got this by running the method below in the lease model.

def balance_to_date(date)
 ...
  rent_logs.where("dated <= ?", date).sum(:credit) - rent_logs.where("dated <= ?" ,date).sum(:debit)
  #problem with above is that it calculates day by day, rather than record by record.
end

The problem is that I don't want it to get a difference of all the prior through out the date of interest. I want it to get the difference of all the prior through the *current record.

There are no other obvious propertys to do conditions or filters on that I can think of. The best solution that I can think of is an ugly one that probably should get me fired...: 

def balance_to_transaction(id)
  balance = rent_logs.where("dated <= ?", date-1.day).sum(:credit) - rent_logs.where("dated <= ?" ,date-1.day).sum(:debit)
  rent_logs.where("dated = ?", date).each do |transaction|
    balance += transaction.credit
    balance -= transaction.debit
    if (id == transaction.id) 
      break
    end
  end
  balance
end

This cannot be the right way to do this?

I'm using Rails 3.2.12, Ruby 1.9.3

Thanks Phil

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1 回答 1

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问题是您使用日期作为条件，这在同一天的记录之间没有区别。要解决此问题，请使用 ID 来区分记录。

def balance_to_item(date, id)
 ...
  rent_logs.where(["dated < ? or (dated = ? and ID <= ?)", date, date, id]).sum(:credit) - 
  rent_logs.where(["dated < ? or (dated = ? and ID <= ?)", date, date, id]).sum(:debit)
end

您需要指定交易项目来计算余额。

于 2013-03-05T09:50:29.793 回答