对某一个action的IP的限制方式是，在routes.rb中：
constraints(:ip => Settings.ip.allow) do
post '/somecontroller/callback', to: 'somecontroller#callback' , as: 'somecontroller_callback'
end
在settings.yml中：
ip:
allow: '127.0.0.1'
这是可以的.
但是想对多个IP允许访问，在settings.yml中如下：
ip:
allow: '/127.0.0.1|127.0.0.2/'
却不行。哪里不对呢？
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Because Settings.ip.allow always returns String, but in fact, in the second case, what you need is a RegExp, so it is invalid. You can try changing it like this:
config/routes.rb:
config/settings.rb