在 Rails 3 中创建哈希

Question

我掌握了一种计算 ISBN 版税的方法。它按销售渠道划分销售额。特许权使用费率由销售总量决定，特许权使用费的计算方法是特许权使用费率（百分比）乘以总收入。因此，结果应该是每个 ISBN 的每个销售渠道的计算版税数字。原谅可能被过度注释的代码。

在 isbns_controller 的 show 方法中：

@isbn = Isbn.find(params[:id])

def royalty(isbn)
  @royaltiesbychannel = Hash.new()     
  # Returns all sales for the current isbn, and groups them by channel_id in a hash 
  # {1 => sale 1, sale 2}, {2 => sale 1, sale 2}
  # Then loops through each key-value pair.    
  @isbn.sales.group_by(&:channel_id).each do |ch_id, sale_array|
    # Takes the sales grouped by channel, and totals the quantities and values into two separate variables. 
    value_total_by_channel = sale_array.sum(&:value)  
    quantity_total_by_channel = sale_array.sum(&:quantity)  
     # Gets all the rules for the isbn
     @isbn.rules.each do |rule|
       # Jumps to the next sales hash unless the channel ids match
       next unless rule.channel_id == ch_id
       if Range.new(rule.lower,rule.upper).include?(quantity_total_by_channel)
         @royaltiesbychannel[ch_id] = value_total_by_channel * rule.rate
       end
     end
   end
 end

最后一行给我带来了问题。我想要的是生成一个哈希值，其中通道 ID 作为键，计算出的版税作为值。但相反，它只生成一个只有一个键值对的散列，看起来像这样：

{1=>#<BigDecimal:10132a620,'0.875E5',9(36)>}

我怀疑我在方法顶部创建新散列的方式有问题，并且尝试声明方括号中的键。

rule.rate 是用小数表示的百分比，例如 0.10。该值是一个整数（至少目前是这样）。关于如何生成这个哈希有什么想法吗？

其次，迭代视图中生成的哈希值的最佳方法是什么？

非常感谢。

更新 - 按要求输出 .inspect：

{1=>[#<Sale id: 1, isbn_id: 2, quantity: 3000, value: 122000, currency: "", total_quantity: nil, created_at: "2011-05-16 19:52:36", updated_at: "2011-05-22 14:28:33", customer: "WHS", retail_price: nil, discount: nil, channel_id: 1, invoice_date: "2011-02-01", rule_id: nil>, #<Sale id: 2, isbn_id: 2, quantity: 500, value: 3000, currency: "", total_quantity: nil, created_at: "2011-05-19 09:55:00", updated_at: "2011-05-19 09:55:00", customer: "Borders", retail_price: nil, discount: nil, channel_id: 1, invoice_date: nil, rule_id: nil>], 2=>[#<Sale id: 6, isbn_id: 2, quantity: 10, value: 2000, currency: "", total_quantity: nil, created_at: "2011-05-19 10:34:34", updated_at: "2011-05-19 11:21:07", customer: "Bookshop a", retail_price: nil, discount: nil, channel_id: 2, invoice_date: nil, rule_id: nil>, #<Sale id: 7, isbn_id: 2, quantity: 2000, value: 4000, currency: "", total_quantity: nil, created_at: "2011-05-19 10:34:49", updated_at: "2011-05-19 10:34:49", customer: "Bookshop b", retail_price: nil, discount: nil, channel_id: 2, invoice_date: nil, rule_id: nil>]}

第二次更新：对问题的修订：

感谢您到目前为止的想法。事实证明，该方法运行良好，因为 @isbn.sales.group_by(&:channel_id) 生成的哈希仅包含一个键值对。所以我的问题仍然存在，但对于我的代码的不同部分：如何在 Sales 模型上执行查找以生成像 {1 =>;销售 1，销售 2}，{2 =>销售 1，销售 2}？

我已经尝试过这个可怕的事情：

@channelarray = Channel.select(:id).all  
@salesbychannelwrong = @channelarray.group_by {|i| Sale.where("channel_id = ?",i).where("isbn_id =?", @isbn)}   
@salesbychannel = @salesbychannelwrong.invert

这给出了这个：

{[#<Channel id: 1>]=>[#<Sale id: 1, isbn_id: 2, quantity: 3000, value: 122000, currency: "", total_quantity: nil, created_at: "2011-05-16 19:52:36", updated_at: "2011-05-22 14:28:33", customer: "WHS", retail_price: nil, discount: nil, channel_id: 1, invoice_date: "2011-02-01", rule_id: nil>, #<Sale id: 2, isbn_id: 2, quantity: 500, value: 3000, currency: "", total_quantity: nil, created_at: "2011-05-19 09:55:00", updated_at: "2011-05-19 09:55:00", customer: "Borders", retail_price: nil, discount: nil, channel_id: 1, invoice_date: nil, rule_id: nil>], [#<Channel id: 2>]=>[#<Sale id: 6, isbn_id: 2, quantity: 10, value: 2000, currency: "", total_quantity: nil, created_at: "2011-05-19 10:34:34", updated_at: "2011-05-19 11:21:07", customer: "Bookshop a", retail_price: nil, discount: nil, channel_id: 2, invoice_date: nil, rule_id: nil>, #<Sale id: 7, isbn_id: 2, quantity: 2000, value: 4000, currency: "", total_quantity: nil, created_at: "2011-05-19 10:34:49", updated_at: "2011-05-19 10:34:49", customer: "Bookshop b", retail_price: nil, discount: nil, channel_id: 2, invoice_date: nil, rule_id: nil>]}

我也尝试过

Sale.find_by_isbn_id(:id).group_by(&:channel_id)

返回nil

并且

Sale.find_by_isbn_id(@isbn).group_by(&:channel_id)

返回

undefined method `group_by' for #<Sale:0x0000010122df60>

我有以下模型：

class Sale
  belongs_to :isbn
  belongs_to :channel
  ...
end

class Isbn
  has_many :rules
  has_many :sales
  has_many :channels, :through => :sales
  ...
end

class Channel
  has_many :sales
  has_many :rules
  ...
end

class Rule
  belongs_to :isbn
  belongs_to :channel
  has_many :sales, :through => :isbn
  ...
end

再次感谢。

Answer 1

Sale.find_by_isbn_id(@isbn).group_by(&:channel_id) =>; Sale.find_all_by_isbn_id(@isbn).group_by(&:channel_id)

或

Sale.where(:ibn_id => @isbn.id).group_by(&:channel_id)