如何在 rails 引擎中升级 'arel' gem,Ryan Bigg 的书

how to upgrade 'arel' gem in a rails engine, Ryan Bigg's book

我尝试将以下 link 添加到我的 gemspec 中:

  s.add_dependency 'arel', '6.0.0.beta2'

然后当我运行 bundle 时我得到

Bundler could not find compatible versions for gem "arel":
  In Gemfile:
    subscribem (>= 0) ruby depends on
      rails (~> 4.2.0) ruby depends on
        activerecord (= 4.2.0) ruby depends on
          arel (~> 6.0) ruby

    subscribem (>= 0) ruby depends on
      arel (6.0.0.beta2)

我需要更新 arel,因为它会导致一些已知的迁移错误 here

好的,这成功了:

sudo gem install arel -v 6.0.0.beta2