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"

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"

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}

把它放到初始化式中

class Hash
  def filter(*args)
    return nil if args.try(:empty?)
    if args.size == 1
      args[0] = args[0].to_s if args[0].is_a?(Symbol)
      self.select {|key| key.to_s.match(args.first) }
    else
      self.select {|key| args.include?(key)}
    end
  end
end

然后你就可以

{a: "1", b: "b", c: "c", d: "d"}.filter(:a, :b) # =>  {a: "1", b: "b"}

or

{a: "1", b: "b", c: "c", d: "d"}.filter(/^a/)  # =>  {a: "1"}

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)。

关于奖金问题:

If you have output from #select method like this (list of 2-element arrays): [[:choice1, "Oh look, another one"], [:choice2, "Even more strings"], [:choice3, "But wait"]] then simply take this result and execute: filtered_params.join("\t") # or if you want only values instead of pairs key-value filtered_params.map(&:last).join("\t") If you have output from #delete_if method like this (hash): {:choice1=>"Oh look, another one", :choice2=>"Even more strings", :choice3=>"But wait"} then: filtered_params.to_a.join("\t") # or filtered_params.values.join("\t")