What is the best way for getting difference between records' column

Question

I have a model CounterRecord and column there data . Records list:

r1.data = 10
r2.data = 12
r3.data = 15
r4.data = 20

I would like to get differences between current and previous record [10,2,3,5] . Does Rails have default way do that?

Answer 1

我不认为Rails或ActiveRecord有这样的东西，但是只需一点点红宝石就可以轻松实现：

CounterRecord.pluck(:data).each_with_index.map { |c,i| a[0] == c ? c : (a[i-1].to_i - c).abs }

Answer 2

Do the rails have default way do that?

No.

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Possible solution:

CounterRecord.pluck(:data).each_cons(2).map { |first, second| second - first }

NOTE: with big amount of records this will easily kill your memory.

Answer 3

没有默认的方法可以这样做。