在Ruby中循环使用多个数组

Question

我有多ActiveRecord个子类实例数组Item,我需要根据最早的事件循环打印.在这种情况下,我需要打印打印付款和维护日期如下:

项目5天内需要维护
项目B 6天内
需要付款
项目7天内需要付款项目B维护需要8天

我目前有两个查询maintenance和payment项目查询(非独占查询)和以下输出它们:

<%- item_p = nil -%>
<%- item_m = nil -%>

<%- loop do -%>
  <% item_p ||= @items_p.shift %>
  <% item_m ||= @items_m.shift %>

  <%- if item_p.nil? and item_m.nil? then break -%>
  <%- elsif item_p and (item_m.nil? or item_p.paymt < item_m.maint) then -%>
    <%= item_p.name %> payment required in ...
  <%- elsif item_m and (item_p.nil? or item_m.maint < item_p.paymt) then -%>
    <%= item_m.name %> maintenance required in ...
  <%- end -%>
<%- end -%>

有什么方法可以清除上面(丑陋)代码的可读性？

Answer 1

拥抱鸭子打字并确保你的对象是多态的.您希望您的付款项目与维护项目相当,以便对其进行排序.

所以,假设你有一个Payment和一个Maintenance类:

module Due
  include Comparable

  # Compare this object with another. Used for sorting.
  def <=>(other)
    self.due <=> other.due
  end
end

class Payment < ActiveRecord::Base
  include Due

  alias_method :due, :payment

  def action
    "#{name} requires payment"
  end
end

class Maintenance < ActiveRecord::Base
  include Due

  alias_method :due, :maintenance

  def action
    "#{name} requires maintenance"
  end
end

看看我们如何创建一个action,due并<=>在方法两个班？我们还注意包含Ruby内置模块Comparable.这允许我们执行以下操作:

# Assuming 'payment' and 'maintenance' are date fields...
a = Payment.new :payment => 3.days.from_now
b = Maintenance.new :maintenance => 2.days.from_now
[a, b].sort
#=> [b, a]

然后视图变得如此简单:

<% (@payment_items + @maintenance_items).sort.each do |item| %>
  <%= item.action %> in <%= distance_of_time_in_words_to_now(item.due) %><br/>
<% end %>

我确定我没有正确的实施细节,但我希望这能让您了解如何处理您的问题.

Answer 2

这是快速且肮脏的（即未优化）：

# In your controller:
@items = @items_p.map{ |item| {:item => item, :days => item.paymt, :description => "payment"} } 
@items += @items_m.map{ |item| {:item => item, :days => item.maint, :description => "maintenance"} }
@items = @items.sort_by{ |item| item[:day] }

# In your view:
<% @items.each do |item| %>
  <%= item[:item].name %> <%= item[:description] %> required in <%= item[:days] %> days
<% end %>