通过升序和降序对多个值进行排序

Question

我正在尝试根据不同的属性对一组对象进行排序.其中一些属性我想按升序排序,有些属性按降序排序.我已经能够按升序或降序排序,但却无法将两者结合起来.

这是我正在使用的简单课程:

class Dog
  attr_reader :name, :gender

  DOGS = []

  def initialize(name, gender)
    @name = name
    @gender = gender
    DOGS << self
  end

  def self.all
    DOGS
  end

  def self.sort_all_by_gender_then_name
    self.all.sort_by { |d| [d.gender, d.name] }
  end
end

然后,我可以实例化一些狗,以便稍后进行分类.

@rover = Dog.new("Rover", "Male")
@max = Dog.new("Max", "Male")
@fluffy = Dog.new("Fluffy", "Female")
@cocoa = Dog.new("Cocoa", "Female")

然后我可以使用sort_all_by_gender_then_name方法.

Dog.sort_all_by_gender_then_name
=> [@cocoa, @fluffy, @max, @rover]

它返回的数组首先包括女性,然后是男性,所有数据都按名称按升序排序.

但是,如果我想让性别下降,然后命名升序,那么它将首先是男性,然后按名称升序排序.在这种情况下:

=> [@max, @rover, @cocoa, @fluffy]

或者,如果我想按性别提升,但名称下降:

=> [@fluffy, @cocoa, @rover, @max]

在对数值进行排序时,您可以预先添加 - 以使其反向排序.但是,我一直无法找到使用字符串执行此操作的方法.任何帮助或想法将不胜感激.谢谢.

Answer 1

这是使用.sort而不是使用的一种方法.sort_by:

dogs = [
  { name: "Rover", gender: "Male" },
  { name: "Max", gender: "Male" },
  { name: "Fluffy", gender: "Female" },
  { name: "Cocoa", gender: "Female" }
]

# gender asc, name asc
p(dogs.sort do |a, b|
  [a[:gender], a[:name]] <=> [b[:gender], b[:name]]
end)

# gender desc, name asc
p(dogs.sort do |a, b|
  [b[:gender], a[:name]] <=> [a[:gender], b[:name]]
end)

# gender asc, name desc
p(dogs.sort do |a, b|
  [a[:gender], b[:name]] <=> [b[:gender], a[:name]]
end)

输出:

[{:name=>"Cocoa", :gender=>"Female"}, {:name=>"Fluffy", :gender=>"Female"}, {:name=>"Max", :gender=>"Male"}, {:name=>"Rover", :gender=>"Male"}]
[{:name=>"Max", :gender=>"Male"}, {:name=>"Rover", :gender=>"Male"}, {:name=>"Cocoa", :gender=>"Female"}, {:name=>"Fluffy", :gender=>"Female"}]
[{:name=>"Fluffy", :gender=>"Female"}, {:name=>"Cocoa", :gender=>"Female"}, {:name=>"Rover", :gender=>"Male"}, {:name=>"Max", :gender=>"Male"}]

基本上,如果需要按降序排序,通过将属性交换到另一个元素,这类似于否定数字(如您在问题中所提到的).