我如何为 nil:NilClass 解决这个未定义的方法“[]”并在模板文件中调用结果

Question

我有一个 table 有很多数据（交易数据），我想对其进行综合报告。这个table有Currency、Fee charged、Network Fee Charged、Order Type、Created_at、Updated_at。例如，在这份报告中，我想根据选择的日期时间范围计算 fees 的总和，如果没有选择日期时间，则默认为 30 天，并根据数据库中的所有唯一货币计算费用总和 table .

在实现这一点时，这就是我所做的，它不起作用，但遇到了 undefined method `[]' for nil:NilClass Error。

module Admin
  module Statistic
    class RevenuesController < BaseController
      def show
        @revenues_grid = ::Statistic::RevenuesGrid.new(params[:statistic_revenues_grid])
        @revenues_reports = []
        Currency.all.each do |currency|
          start_datetime = params.nil? ? 30.days.ago : params[:created_at][0] # This throws the error
          end_datetime = params.nil? ? Time.now : params[:created_at][1] # This throws the error too
          revenues_report_for_currency = get_revenue_report_for_currency(currency, start_datetime, end_datetime)
          @revenues_reports << revenues_report_for_currency
        end
      end

      def get_revenue_report_for_currency(currency, start_datetime, end_datetime)
        total_withdraw_fees_charged = Withdraw.where(:currency => currency.id, :created_at => start_datetime..end_datetime).sum(:fee)
        total_withdraw_network_fees_charged= 0.3 * total_withdraw_fees_charged
        net_income_from_withdraws = total_withdraw_fees_charged - total_withdraw_network_fees_charged

        total_sell_order_fees_charged = Order.where(:type => 'OrderAsk', :bid => currency.id, :created_at => start_datetime..end_datetime).sum(:fee)
        total_buy_order_fees_charged = Order.where(:type => 'OrderBid', :ask => currency.id, :created_at => start_datetime..end_datetime).sum(:fee)
        total_trading_fees = total_sell_order_fees_charged + total_buy_order_fees_charged

        total_fees = net_income_from_withdraws + total_trading_fees

        {
          :total_withdraw_fees_charged =>  total_withdraw_fees_charged,
          :total_withdraw_network_fees_charged =>  total_withdraw_network_fees_charged,
          :net_income_from_withdraws =>  net_income_from_withdraws,
          :total_sell_order_fees_charged =>  total_sell_order_fees_charged,
          :total_buy_order_fees_charged =>  total_buy_order_fees_charged,
          :total_trading_fees =>  total_trading_fees,
          :total_fees => total_fees
        }
      end
    end
  end
end

我该如何解决这个问题undefined method `[]' for nil:NilClass Error？

Answer 1

在行start_datetime = params.nil? ? 30.days.ago : params[:created_at][0]

中更改params.nil?

成为params[:created_at].nil?

更改后的代码将是：

module Admin
  module Statistic
    class RevenuesController < BaseController
      def show
        @revenues_grid = ::Statistic::RevenuesGrid.new(params[:statistic_revenues_grid])
        @revenues_reports = []
        Currency.all.each do |currency|
          start_datetime = params[:created_at].nil? ? 30.days.ago : params[:created_at][0] # This shouldn't throw error
          end_datetime = params[:created_at].nil? ? Time.now : params[:created_at][1] # This shouldn't throw error
          revenues_report_for_currency = get_revenue_report_for_currency(currency, start_datetime, end_datetime)
          @revenues_reports << revenues_report_for_currency
        end
      end

      def get_revenue_report_for_currency(currency, start_datetime, end_datetime)
        total_withdraw_fees_charged = Withdraw.where(:currency => currency.id, :created_at => start_datetime..end_datetime).sum(:fee)
        total_withdraw_network_fees_charged= 0.3 * total_withdraw_fees_charged
        net_income_from_withdraws = total_withdraw_fees_charged - total_withdraw_network_fees_charged

        total_sell_order_fees_charged = Order.where(:type => 'OrderAsk', :bid => currency.id, :created_at => start_datetime..end_datetime).sum(:fee)
        total_buy_order_fees_charged = Order.where(:type => 'OrderBid', :ask => currency.id, :created_at => start_datetime..end_datetime).sum(:fee)
        total_trading_fees = total_sell_order_fees_charged + total_buy_order_fees_charged

        total_fees = net_income_from_withdraws + total_trading_fees

        {
          :total_withdraw_fees_charged =>  total_withdraw_fees_charged,
          :total_withdraw_network_fees_charged =>  total_withdraw_network_fees_charged,
          :net_income_from_withdraws =>  net_income_from_withdraws,
          :total_sell_order_fees_charged =>  total_sell_order_fees_charged,
          :total_buy_order_fees_charged =>  total_buy_order_fees_charged,
          :total_trading_fees =>  total_trading_fees,
          :total_fees => total_fees
        }
      end
    end
  end
end

更好的方法是替换

start_datetime = params[:created_at].nil? ? 30.days.ago : params[:created_at][0]
end_datetime = params[:created_at].nil? ? Time.now : params[:created_at][1]

和

start_datetime, end_datetime = params[:created_at].nil? ? [30.days.ago, Time.now] : params[:created_at]

我如何为 nil:NilClass 解决这个未定义的方法“[]”并在模板文件中调用结果

how do i solve this undefined method `[]' for nil:NilClass and call the result in the template file

ruby

ruby-on-rails

ruby-on-rails-4