将数组的哈希值与另一个数组进行比较以查找相似性

Question

我试图比较所选的animal_id数组到owners_to_animals数组中的"animal_id"对象，这样我就可以有一个只包含相关owner_id的列表。我试图通过散列迭代，然后只选择在animal_id数组中匹配的animal_id对象，但它打印出animal_id=20，这不是animal_id数组的一部分。

animal_id = [23, 53, 63]
owners_to_animals = [
  { "owner_id" => 73, "animal_id" => 53 },
  { "owner_id" => 73, "animal_id" => 23 },
  { "owner_id" => 73, "animal_id" => 63 },
  { "owner_id" => 73, "animal_id" => 20 },
  { "owner_id" => 83, "animal_id" => 23 },
  { "owner_id" => 83, "animal_id" => 63 }
]
owners_to_animals.each do |x|
  # puts x
  # x.each do |y|
  for i in animal_id do
    # puts i
    if x.select { |a| a["animal_id"] == i }
      puts x
    else
      puts "no"
    end
  end
  # end
end

我很困惑为什么x返回:

{"owner_id"=>73, "animal_id"=>53}
{"owner_id"=>73, "animal_id"=>53}
{"owner_id"=>73, "animal_id"=>53}
{"owner_id"=>73, "animal_id"=>23}
{"owner_id"=>73, "animal_id"=>23}
{"owner_id"=>73, "animal_id"=>23}
{"owner_id"=>73, "animal_id"=>63}
{"owner_id"=>73, "animal_id"=>63}
{"owner_id"=>73, "animal_id"=>63}
{"owner_id"=>73, "animal_id"=>20}
{"owner_id"=>73, "animal_id"=>20}
{"owner_id"=>73, "animal_id"=>20}
{"owner_id"=>83, "animal_id"=>23}
{"owner_id"=>83, "animal_id"=>23}
{"owner_id"=>83, "animal_id"=>23}
{"owner_id"=>83, "animal_id"=>63}
{"owner_id"=>83, "animal_id"=>63}
{"owner_id"=>83, "animal_id"=>63}

Answer 1

select将返回一个空数组，如果没有匹配，这在Ruby中是一个" true "值，所以你的代码的else分支永远不会执行。

if []
  puts "true"
else
  puts "false"
end
# Outputs "true"

你想要达到的效果可以在一行中完成:

puts owners_to_animals.select { |x| animal_id.include?(x["animal_id"]) }
# Output:
{"owner_id"=>73, "animal_id"=>53}
{"owner_id"=>73, "animal_id"=>23}
{"owner_id"=>73, "animal_id"=>63}
{"owner_id"=>83, "animal_id"=>23}
{"owner_id"=>83, "animal_id"=>63}