如何在Ruby中扁平化嵌套哈希

def flatten_hash(hash, prefix = '')
  flat_hash = {}
  hash.each do |key, value|
    new_key = prefix.empty? ? key.to_s : "#{prefix}.#{key}"
    if value.is_a?(Hash)
      flat_hash.merge!(flatten_hash(value, new_key))
    else
      flat_hash[new_key] = value
    end
  end
  flat_hash
end

nested_hash = {
  name: 'John',
  age: 30,
  address: {
    street: '123 Main St',
    city: 'New York',
    country: 'USA'
  }
}

flat_hash = flatten_hash(nested_hash)
puts flat_hash.inspect

{
  "name"=>"John",
  "age"=>30,
  "address.street"=>"123 Main St",
  "address.city"=>"New York",
  "address.country"=>"USA"
}