Question

我有一个像hash = {"band" => "for King & Country", "song_name" => "Matter"}这样的哈希和一个类：

class Song
  def initialize(*args, **kwargs)
    #accept either just args or just kwargs
    #initialize @band, @song_name
  end
end

我想传递hash作为关键字参数，例如Song.new band: "for King & Country", song_name: "Matter"是否可能？

Answer 1

您必须将哈希中的键转换为符号：

class Song
  def initialize(*args, **kwargs)
    puts "args = #{args.inspect}"
    puts "kwargs = #{kwargs.inspect}"
  end
end

hash = {"band" => "for King & Country", "song_name" => "Matter"}

Song.new(hash)
# Output:
# args = [{"band"=>"for King & Country", "song_name"=>"Matter"}]
# kwargs = {}

symbolic_hash = hash.map { |k, v| [k.to_sym, v] }.to_h
#=> {:band=>"for King & Country", :song_name=>"Matter"}

Song.new(symbolic_hash)
# Output:
# args = []
# kwargs = {:band=>"for King & Country", :song_name=>"Matter"}

在Rails / Active Support中有Hash#symbolize_keys

Answer 2

正如Stefan所提到的，在Rails中，我们可以访问symbolize_keys，其工作方式如下：

{"band" => "for King & Country", "song_name" => "Matter"}.symbolize_keys
#=> {:band=>"for King & Country", :song_name=>"Matter"}

它的别名也为：to_options，因此：

{"band" => "for King & Country", "song_name" => "Matter"}.to_options
#=> {:band=>"for King & Country", :song_name=>"Matter"}

将哈希传递给接受关键字参数的函数

2 个答案: