在评论中澄清你的问题（与标题无关）：

Answering your question as clarified in comments (which has nothing to do with the title):

我需要将字符串编码/解码为Base58

I need to encode/decode a string to Base58

编辑：现在作为一个类（使用base58 gem）：

now as a class (using base58 gem):

require 'base58'

class Base58ForStrings
  def self.encode(str)
    Base58.encode(str.bytes.inject { |a, b| a * 256 + b })
  end

  def self.decode(b58)
    b = []
    d = Base58.decode(b58)
    while (d > 0)
      d, m = d.divmod(256)
      b.unshift(m)
    end
    b.pack('C*').force_encoding('UTF-8')
  end
end

Base58ForStrings.encode('Hello こんにちは')
# => "5scGDXBpe3Vq7szFXzFcxHYovbD9c" 
Base58ForStrings.decode('5scGDXBpe3Vq7szFXzFcxHYovbD9c')
# => "Hello こんにちは"

适用于任何UTF-8字符串。

Works for any UTF-8 string.