Ruby Gemspec中的条件依赖项 [英] Conditional Dependency in Ruby Gemspec

问题描述

我正在构建一个需要安装json gem才能工作的gem。无论哪个json gem：json_pure，json-jruby或基于C的json。

有没有在gemspec中定义这个好方法？ 此回复建议为每个版本保留一个完全独立的gem，但似乎必须有一个更好的方式。

有没有人有这方面的经验？

我应该只使用 spec.requirements 选项可以让用户注意到他/她需要一个json宝石？

解决方案

是的，我建议在 spec.requirements 。在gem第一次加载时，我还会推荐一些加载链接：

 ＃init.rb和/或rails / init.rb：
除非Object.const_defined？（：JSON）
 begin 
 require'json_pure'
 rescue LoadError 
 begin 
 require'json-ruby '
 rescue LoadError 
 require'json'
 end 
 end 
 end 
除非Object.const_defined？（：JSON）
 raise可能不加载gem MyGem;你安装了json_pur，json-ruby还是基于C的json库？ 
 end 
  

I'm building a gem that needs a json gem installed in order for it to work. It doesn't matter which json gem: json_pure, json-jruby, or the C-based json.

Is there a good way of defining this in a gemspec? This response suggests maintaining a completely separate gem for each version, but it seems like there has got to be a better way.

Does anybody have any experience with this?

Should I just use the spec.requirements option to give the user a notice that he/she needs a json gem?

解决方案

Yes, I would suggest a simple text requirement in spec.requirements. I would also recommend some sort of load-chaining when the gem first loads:

# in init.rb and/or rails/init.rb:
unless Object.const_defined?(:JSON)
  begin
    require 'json_pure'
  rescue LoadError
    begin
      require 'json-ruby'
    rescue LoadError
      require 'json'
    end
  end
end
unless Object.const_defined?(:JSON)
  raise "Could not load gem MyGem; did you install one of json_pur, json-ruby, or the C-based json library?"
end

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