2.6.3 :001 > hash = {:a => "a", :b => ["c", "d", "e"]}
=> {:a=>"a", :b=>["c", "d", "e"]}
2.6.3 :002 > hash.to_a.map { |x| "#{x[0]}=#{x[1].class == Array ? x[1].join(",") : x[1]}" 
}.join("&")
=> "a=a&b=c,d,e"

偷Merb的东西:

# File merb/core_ext/hash.rb, line 87
def to_params
  params = ''
  stack = []

  each do |k, v|
    if v.is_a?(Hash)
      stack << [k,v]
    else
      params << "#{k}=#{v}&"
    end
  end

  stack.each do |parent, hash|
    hash.each do |k, v|
      if v.is_a?(Hash)
        stack << ["#{parent}[#{k}]", v]
      else
        params << "#{parent}[#{k}]=#{v}&"
      end
    end
  end

  params.chop! # trailing &
  params
end

参见http://noobkit.com/show/ruby/gems/development/merb/hash/to_params.html

class Hash
  def to_params
    params = ''
    stack = []

    each do |k, v|
      if v.is_a?(Hash)
        stack << [k,v]
      elsif v.is_a?(Array)
        stack << [k,Hash.from_array(v)]
      else
        params << "#{k}=#{v}&"
      end
    end

    stack.each do |parent, hash|
      hash.each do |k, v|
        if v.is_a?(Hash)
          stack << ["#{parent}[#{k}]", v]
        else
          params << "#{parent}[#{k}]=#{v}&"
        end
      end
    end

    params.chop! 
    params
  end

  def self.from_array(array = [])
    h = Hash.new
    array.size.times do |t|
      h[t] = array[t]
    end
    h
  end

end

最好的方法是使用Hash。To_params可以很好地处理数组。

{a: 1, b: [1,2,3]}.to_param
"a=1&b[]=1&b[]=2&b[]=3"

更新:此功能已从gem中移除。

朱利安，你自己的回答很好，我无耻地借鉴了它，但它不能正确地逃脱保留字符，还有一些其他的边缘情况，它会崩溃。

require "addressable/uri"
uri = Addressable::URI.new
uri.query_values = {:a => "a", :b => ["c", "d", "e"]}
uri.query
# => "a=a&b[0]=c&b[1]=d&b[2]=e"
uri.query_values = {:a => "a", :b => [{:c => "c", :d => "d"}, {:e => "e", :f => "f"}]}
uri.query
# => "a=a&b[0][c]=c&b[0][d]=d&b[1][e]=e&b[1][f]=f"
uri.query_values = {:a => "a", :b => {:c => "c", :d => "d"}}
uri.query
# => "a=a&b[c]=c&b[d]=d"
uri.query_values = {:a => "a", :b => {:c => "c", :d => true}}
uri.query
# => "a=a&b[c]=c&b[d]"
uri.query_values = {:a => "a", :b => {:c => "c", :d => true}, :e => []}
uri.query
# => "a=a&b[c]=c&b[d]"

宝石是“可寻址的”

gem install addressable

我知道这是一个老问题，但我只是想张贴这段代码，因为我找不到一个简单的宝石来为我做这个任务。

module QueryParams

  def self.encode(value, key = nil)
    case value
    when Hash  then value.map { |k,v| encode(v, append_key(key,k)) }.join('&')
    when Array then value.map { |v| encode(v, "#{key}[]") }.join('&')
    when nil   then ''
    else            
      "#{key}=#{CGI.escape(value.to_s)}" 
    end
  end

  private

  def self.append_key(root_key, key)
    root_key.nil? ? key : "#{root_key}[#{key.to_s}]"
  end
end

在这里汇总为宝石:https://github.com/simen/queryparams