blocks|key|1590506|text|您可以只使用内置的Hash函数reject。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1590507|x+=+{+"one"+=>+"one",+"two"+=>+"two",+"three"+=>+"three"}
y+=+x.reject+{%7Ckey,value%7C+key+==+"three"+}
y+==+{+"one"+=>+"one",+"two"+=>+"two"}|code-block|syntax|javascript|1590508|你可以把任何你想要的逻辑放到reject中，如果代码块返回true，它将跳过新散列中的键和值。|1590509|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You can just use the built in Hash function reject.

<pre><code>x = { "one" =&gt; "one", "two" =&gt; "two", "three" =&gt; "three"}
y = x.reject {|key,value| key == "three" }
y == { "one" =&gt; "one", "two" =&gt; "two"}
</code></pre>

You can put whatever logic you want into the reject, and if the block returns true it will skip that key,value in the new hash.

blocks|key|1590520|text|y+=+x.reject+{%7Ck,v%7C+k+==+"three"}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1590521|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>y = x.reject {|k,v| k == "three"}
</code></pre>

blocks|key|1590584|text|也许这就是你想要的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1590585|wanted_keys+=+%25w[one+two]
x+=+{+"one"+=>+"one",+"two"+=>+"two",+"three"+=>+"three"}
x.select+{+%7Ckey,_%7C+wanted_keys.include?+key+}|code-block|syntax|javascript|1590586|例如，Array和Hash中包含的可枚举的mixin提供了许多有用的方法，如select/reject/each/等。我建议您使用ri+Enumerable查看它的文档。|1590587|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Maybe this it what you want.

<pre><code>wanted_keys = %w[one two]
x = { "one" =&gt; "one", "two" =&gt; "two", "three" =&gt; "three"}
x.select { |key,_| wanted_keys.include? key }
</code></pre>

The Enumerable mixin which is included in e.g. Array and Hash provides a lot of useful methods like select/reject/each/etc.. I suggest that you take a look at the documentation for it with ri Enumerable.

blocks|key|1375388|text|综合每个人的答案，我想出了这个解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1375389|+wanted_keys+=+%25w[one+two]
+x+=+{+"one"+=>+"one",+"two"+=>+"two",+"three"+=>+"three"}
+x.reject+{+%7Ckey,_%7C+!wanted_keys.include?+key+}
+=>{+"one"+=>+"one",+"two"+=>+"two"}|code-block|syntax|javascript|1375390|谢谢你们的帮助！|1375391|编辑：|1375392|上面的代码可以在1.8.7%2B中运行|1375393|以下内容适用于1.9%2B：|1375394|密钥{+%7Ckey，_%7C+wanted_keys.include?+x.select+{%7Ckey，_%7Cwanted_keys.include？密钥}|1375395|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

Using a combination of everyone's answers I have come up with this solution:

<pre><code> wanted_keys = %w[one two]
 x = { "one" =&gt; "one", "two" =&gt; "two", "three" =&gt; "three"}
 x.reject { |key,_| !wanted_keys.include? key }
 =&gt;{ "one" =&gt; "one", "two" =&gt; "two"}
</code></pre>

Thanks for your help guys!

EDIT: 

The above works in 1.8.7+ 

The following works in 1.9+ :

x.select { |key,_| wanted_keys.include? key }

blocks|key|1375475|text|Rails的ActiveSupport库还为您提供了切片，除了处理键级别的散列之外：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1375476|y+=+x.slice("one",+"two")+#+=>+{+"one"+=>+"one",+"two"+=>+"two"+}
y+=+x.except("three")+++++#+=>+{+"one"+=>+"one",+"two"+=>+"two"+}
x.slice!("one",+"two")++++#+x+is+now+{+"one"+=>+"one",+"two"+=>+"two"+}|code-block|syntax|javascript|1375477|这些都很不错，我一直都在用它们。|1375478|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Rails' ActiveSupport library also gives you slice and except for dealing with the hash on a key level:

<pre><code>y = x.slice("one", "two") # =&gt; { "one" =&gt; "one", "two" =&gt; "two" }
y = x.except("three") # =&gt; { "one" =&gt; "one", "two" =&gt; "two" }
x.slice!("one", "two") # x is now { "one" =&gt; "one", "two" =&gt; "two" }
</code></pre>

These are quite nice, and I use them all the time.

blocks|key|1375522|text|改进一下@scottd的答案，如果你正在使用rails，并且有一个你需要的列表，你可以将这个列表扩展为slice中的参数。例如|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1375523|hash+=+{+"one"+=>+"one",+"two"+=>+"two",+"three"+=>+"three"}
keys_whitelist+=+%25W(one+two)
hash.slice(*keys_whitelist)|code-block|syntax|javascript|1375524|在没有rails的情况下，对于任何ruby版本，您都可以执行以下操作：|1375525|hash+=+{+"one"+=>+"one",+"two"+=>+"two",+"three"+=>+"three"}
keys_whitelist+=+%25W(one+two)
Hash[hash.find_all{%7Ck,v%7C+keys_whitelist.include?(k)}]+|1375526|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Improving a bit @scottd answer, if you are using rails and have a list of what you need, you can expand the list as parameters from slice. For example

<pre><code>hash = { "one" =&gt; "one", "two" =&gt; "two", "three" =&gt; "three"}
keys_whitelist = %W(one two)
hash.slice(*keys_whitelist)
</code></pre>

And without rails, for any ruby version, you can do the following:

<pre><code>hash = { "one" =&gt; "one", "two" =&gt; "two", "three" =&gt; "three"}
keys_whitelist = %W(one two)
Hash[hash.find_all{|k,v| keys_whitelist.include?(k)}] 
</code></pre>

blocks|key|1590814|text|我会使用lambda来过滤。这将允许您编写复杂的过滤逻辑，并使其易于测试。提取过滤逻辑的事实将允许在其他上下文中重用它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1590815|例如：|1590816|x+=+{+"one"+=>+"one",+"two"+=>+"two",+"three"+=>+"three"}

matcher+=+->(key,value)+{+
++#+FILTERING+LOGIC+HERE+
+++!key[/three/]
}

x.select(&matcher)+==+{+"one"+=>+"one",+"two"+=>+"two"}|code-block|syntax|javascript|1590817|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I'd use a lambda to filter. This will both allow you to write complex filtering logic &amp; make it easy to test it. The fact that the filtering logic is extracted will allow to reuse it in other contexts. 

ex: 

<pre><code>x = { "one" =&gt; "one", "two" =&gt; "two", "three" =&gt; "three"}

matcher = -&gt;(key,value) { 
 # FILTERING LOGIC HERE 
 !key[/three/]
}

x.select(&amp;matcher) == { "one" =&gt; "one", "two" =&gt; "two"}
</code></pre>

I am trying to figure out how I can filter out key and value pairs from one filter into another

For example I want to take this hash

<pre><code>x = { "one" =&gt; "one", "two" =&gt; "two", "three" =&gt; "three"}

y = x.some_function

y == { "one" =&gt; "one", "two" =&gt; "two"}
</code></pre>

Thanks for your help

EDIT: should probably mention that in this example, I want it to behave as a whitelist filter. That is, I know what I want, not what I don't want.

Ruby Hash Whitelist Filter

我正在尝试弄清楚如何将键和值对从一个过滤器中过滤到另一个过滤器中。例如，我想使用这个散列x = { "one" => "one", "two" => "two", "three" => "three"}y = x.some_functiony == { "one" => "one", "two" => "two"}谢谢...

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