params = { :irrelevant => "A String",
           :choice1 => "Oh look, another one",
           :choice2 => "Even more strings",
           :choice3 => "But wait",
           :irrelevant2 => "The last string" }

choices = params.select { |key, value| key.to_s[/^choice\d+/] }
#=> {:choice1=>"Oh look, another one", :choice2=>"Even more strings", :choice3=>"But wait"}

在Ruby中，hash# select是一个正确的选项。如果你使用Rails，你可以使用Hash#slice和Hash#slice!例:(rails 3.2.13)

h1 = {:a => 1, :b => 2, :c => 3, :d => 4}

h1.slice(:a, :b)         # return {:a=>1, :b=>2}, but h1 is not changed

h2 = h1.slice!(:a, :b)   # h1 = {:a=>1, :b=>2}, h2 = {:c => 3, :d => 4}

如果你想要剩下的哈希值:

params.delete_if {|k, v| ! k.match(/choice[0-9]+/)}

或者如果你只是想要钥匙:

params.keys.delete_if {|k| ! k.match(/choice[0-9]+/)}

如果你使用rails并且你在一个单独的列表中有键，你可以使用*符号:

keys = [:foo, :bar]
hash1 = {foo: 1, bar:2, baz: 3}
hash2 = hash1.slice(*keys)
=> {foo: 1, bar:2}

正如其他答案所述，你也可以使用slice!修改哈希(并返回擦除的键/值)。

使用散列切片

{ a: 1, b: 2, c: 3, d: 4 }.slice(:a, :b)
# => {:a=>1, :b=>2}

# If you have an array of keys you want to limit to, you should splat them:
valid_keys = [:mass, :velocity, :time]
search(options.slice(*valid_keys))

这是一条解决完整原始问题的直线:

params.select { |k,_| k[/choice/]}.values.join('\t')

但是上面的大多数解决方案都是使用slice或简单的regexp来解决需要提前知道键的情况。

下面是另一种适用于简单和更复杂用例的方法，它在运行时是可切换的

data = {}
matcher = ->(key,value) { COMPLEX LOGIC HERE }
data.select(&matcher)

现在，这不仅允许在匹配键或值时使用更复杂的逻辑，而且也更容易测试，并且可以在运行时交换匹配逻辑。

解决原问题:

def some_method(hash, matcher) 
  hash.select(&matcher).values.join('\t')
end

params = { :irrelevant => "A String",
           :choice1 => "Oh look, another one",
           :choice2 => "Even more strings",
           :choice3 => "But wait",
           :irrelevant2 => "The last string" }

some_method(params, ->(k,_) { k[/choice/]}) # => "Oh look, another one\\tEven more strings\\tBut wait"
some_method(params, ->(_,v) { v[/string/]}) # => "Even more strings\\tThe last string"