试试不就知道了

会往下执行的，除非有 return

感谢大虾赐教，不过我定义了一个用于 before_action 调用的方法，貌似不用 return 也会退出

def only_post_method
    if request.method != 'POST'
        render plain: '只允许post提交'
    end
end

before_action :only_post_method, :only => [:create, :update]

多查查文档吧 If a "before" filter renders or redirects, the action will not run. If there are additional filters scheduled to run after that filter, they are also cancelled.

http://guides.rubyonrails.org/action_controller_overview.html#filters

感谢大虾指点迷津🙏，看来我在文档阅读上还有欠缺