Question

我有以下哈希类别：

categories = {"horeca" => ["bar", "waiter", "kitchen"], 
              "retail" => ["eerste", "tweede"]}

如果值包含在值数组中，我想找到它们的键。

如下所示

categories.key("bar")

将返回＆＃34; horeca＆＃34;

截至目前我只能得到＆＃34; horeca＆＃34;如果我做

categories.key(["bar", "waiter", "kitchen"])

Answer 1

尝试 Enumberable#find ：

LongRunning

Answer 2

正如Máté所提到的，如果你想找到第一个匹配的元素，可以使用find。如果您想要所有匹配的元素，请使用select。要获得你要做的钥匙：

categories.select { |key, values| values.include?("bar") }.map(&:first)

请参阅https://ruby-doc.org/core-2.2.3/Enumerable.html#method-i-select

Answer 3

Md. Farhan Memon's solution is generally the preferable solution but it has one downside: If there's no match in the collection, it returns the collection itself – which probably isn't a desirable result. You can fix this with a simple adjustment that combines both detect/find and break:

categories.detect { |key, values| break key if values.include?('bar') }

This breaks and returns the value if it finds it and otherwise returns nil (which I assume to be the preferable behavior).

If your collection may also contain nil values and/or non-arrays, you can improve it further:

categories.detect { |key, values| break key if Array(values).include?('bar') }

The only downside of this general approach is that it's not particularly intuitive to newcomers: You have to know a bit more than just basic Ruby to understand what's going on without running the code first.

Answer 4

创建中间数组然后先调用它就没有必要了，如果哈希很大并且你想要第一个匹配的值，那么下面的解决方案就更好了

categories.each{ |k,v| break k if v.include?('bar') }
#=> "horeca"

在哈希中查找数组中的键值

4 个答案: