CODEWITHSUNDEEP
ruby-on-railsrubyactiverecord
pyfl88
pyfl88

Reputation: 1710

Rails: error charting by time

I am creating a chart based on account balance. And here is my some of my codes 

module AccountsHelper
  def products_chart_data
    orders_by_day = Account.total_grouped_by_day(3.days.ago)
    (3.days.ago.to_date..Date.today).map do |date|
      {
        created_at: date,
        balance: orders_by_day[date].first.try(:total_balance) || 0 
      }
    end
  end
end

class Account < ActiveRecord::Base
  belongs_to :user
  has_many :books

  def self.total_grouped_by_day(start)
    balances = where(created_at: start.beginning_of_day..Time.zone.now)
    balances = balances.group("date(created_at)")
    balances = balances.select("created_at, balance as total_balance")
    balances.group_by {|o| o.created_at.to_date }
  end

end

My problems are:

1) I received an error undefined method `first' when mapping 3.days.ago, but successfully run the code when I change it to 2.days.ago. I understand that it is because I do not have data on 3 days ago as this account is new. My question is, how can I rescue this error, because I could have many other new accounts that do not have data yet, and what could I do to display result for 1 month, or 2 month?

Thanks in advance!

Upvotes: 0

Views: 25

Answers (1)

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

#                            ⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓
balance: orders_by_day[date].try(:first).try(:total_balance) || 0

try is the method, introduced by rails and defined on Object class, therefore it is defined on NilClass as well.

The implementation is quite straightforward: it checks whether receiver is empty and returns either the result of the call to it, or nil otherwise.

Upvotes: 1

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