Question

我将自己的方法添加到Array类中，该类与Array＃uniq完全相同。

这是我的版本：

arr = ["fun", "sun", 3, 5, 5, 5, 1, 2, 1, "fun"]

class Array
    def my_uniq
        new_arr = []
        each do |item|
            new_arr << item unless new_arr.include?(item)
        end
        new_arr
    end
end

print arr.my_uniq

有没有办法修改它来返回唯一元素的索引而不是元素本身？

Answer 1

each_with_index将允许您迭代数组并返回索引。

Answer 2

class Array
  def indices_uniq
    uniq.map { |e| index(e) }
  end
end

arr = ["fun", "sun", 3, 5, 5, 5, 1, 2, 1, "fun"]
arr.indices_uniq
  #=> [0, 1, 2, 3, 6, 7]

要了解这里发生了什么，让我们更详细地写一下，并包含一些显示中间值的代码：

class Array
  def indices_uniq
    puts "self = #{self}"
    arr = self
    u = arr.uniq
    puts "u = #{u}"
    u.map { |e|
      puts "#{e} is at index #{index(e)}"
      arr.index(e) }
  end
end

arr.indices_uniq
  # self = ["fun", "sun", 3, 5, 5, 5, 1, 2, 1, "fun"]
  # u = ["fun", "sun", 3, 5, 1, 2]
  # fun is at index 0
  # sun is at index 1
  # 3 is at index 2
  # 5 is at index 3
  # 1 is at index 6
  # 2 is at index 7
  #=> [0, 1, 2, 3, 6, 7]

我们可以替换u和arr：

class Array
  def indices_uniq
    self.uniq.map { |e| self.index(e) }
  end
end

arr.indices_uniq
   #=> [0, 1, 2, 3, 6, 7]

密钥： self是没有显式接收方的方法的接收方。方法的最后一个版本uniq和include都有显式接收者self。因此，如果删除显式接收器，接收器仍然是self：

class Array
  def indices_uniq
    uniq.map { |e| index(e) }
  end
end

arr.indices_uniq
   #=> [0, 1, 2, 3, 6, 7]

另一种方法是将操作线更改为：

map { |e| index(e) }.uniq

Ruby中的猴子修补阵列

2 个答案: