Ruby/Active Record:自定义排序顺序 [英] Ruby / Active Record: custom sorting order

问题描述

我正在开发一个 rails 3.2 ruby​​ 1.9.2 项目.

I'm working on a rails 3.2 ruby 1.9.2 project.

我使用经典从数据库中获取一些值:

I get some values from database with a classic:

designators = Model.find()

我用(简化代码)显示它:

And I show it in view with (simplified code):

<table class="rwy_modes_table" cellspacing='0'>
  <% designators.each do |info_design| %>
    <tr id="rwy_mode_<%=info_design.id%>">
      <td class="spacer"><%= info_design.try(:designator) %></td>
    </tr>
  <% end %>
</table>

值例如:3L、3C、3R.(L 代表左，C 代表中心，4 代表右).我想要排序的值，例如:3L、3C、3R 而不是 3C、3L、3R

Values are for example: 3L, 3C, 3R. (L for Left, C for Center, 4 for Right). I would like values ordered such as: 3L, 3C, 3R and not 3C, 3L, 3R

我不知道如何定义这个自定义订单.有什么想法吗?

I don't know how to define this custom order. Any idea ?

推荐答案

试试这个:

(app/models/designator.rb)
# determines the sort value for based on my_attribute.
# designators should be in the order 'l', 'c', 'r' - regardless of any preceeding numeral
def sort_val
  return 0 if self.my_attribute =~ /l/i
  return 1 if self.my_attribute =~ /c/i
  return 2 if self.my_attribute =~ /r/i
end

(app/helpers/designators_helper.rb)
def sorted_designators(designators)
  designators.sort{|a, b| a.sort_val <=> b.sort_val }
end

您可以在视图中进行排序的位置

Where you can do sorting in your view

(app/views/...)
sorted_designators(designators).each do |design|

或者，您可以将其移动到模型文件中的静态方法中，以便在您的视图之外轻松排序

Alternately, you can move this to a static method in your model file, for easy sorting outside your view

(app/models/designator.rb)
def self.sorted_designators(designators)
  designators.sort{|a, b| a.sort_val <=> b.sort_val }
end

并像这样在控制器中使用它们

and use them in your controller like this

app/controllers...
@designators = Designator.sorted_designators(designators)

注意:这是内存中的排序，因此请注意 O(n) db 查询，具体取决于您排序/访问此对象的方式

Note: this is an in-memory sort, so watch for O(n) db queries depending on how you sort / access this object

另见:https://stackoverflow.com/a/14282353/811255 使用 Comparable 模块(可能更清洁的解决方案)

See also: https://stackoverflow.com/a/14282353/811255 for using the Comparable module (probably a cleaner solution)

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