将数组的散列与数组进行比较以找到相似之处

Question

我正在尝试将 selected animal_id 数组与 owners_to_animals 数组中的 "animal_id" 对象进行比较，这样我就可以得到一个仅包含相关项的列表owner_id 的。我尝试遍历哈希，然后仅 select animal_id 对象在 animal_id 数组中匹配，但它打印出 animal_id=20 不属于 animal_id数组。

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 returns:

{"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

如果没有匹配项，

select 将 return 一个空数组，在 Ruby 中是一个 "truthy" 值，因此代码的 else 分支永远不会被执行。

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

你想实现的可以一行完成：

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}

将数组的散列与数组进行比较以找到相似之处

Comparing a hash of arrays to an array to find similarities

ruby

associative-array

multidimensional-array