Mechanize & Sinatra conflict

问题

I've writter a simple web crawler using Mechanize as a command-line utility. Then I decided to create web app with Sinatra, but got stuck with this error when trying to run the local webserver:

/home/nazar/.rvm/gems/ruby-2.0.0-p195/gems/sinatra-1.4.2/lib/sinatra/base.rb:1569:in `run!': undefined method `run' for HTTP:Module (NoMethodError)
from /home/nazar/.rvm/gems/ruby-2.0.0-p195/gems/sinatra-1.4.2/lib/sinatra/main.rb:25:in `block in <module:Sinatra>'

The source code is dead simple:

require 'sinatra'
require 'mechanize'

get '/' do
   # mechanize stuff
end

I've gone through some investigation and managed to find out that 2 gems work fine separately, but only combining them causes the issue. Can anyone point out what the problem might be?

回答1:

Most probably you are are overriding methods like get with mechanize. Try to wrap your Sinatra application into an application class. That may resolve the issue.

require 'sinatra/base'

class MyApp < Sinatra::Base
  get '/' do
    # mechanize stuff
  end
end

Find out more about that approach in the Sinatra documentation.

回答2:

I had the same issue and was able to solve it by installing and using Thin as my local webserver.

I dug into sinatra source and see that it tries to guess what server to use when running, in order, which you can see via irb:

1.9.3p194 :011 > require 'sinatra'
 => true 
1.9.3p194 :012 > Sinatra::Base
 => Sinatra::Base 
1.9.3p194 :014 > Sinatra::Base::server
 => ["thin", "puma", "HTTP", "webrick"]

Normally Sinatra would fall back to webrick but Mechanize has a Module named HTTP so it tries to use that as a server, which doesn't work of course.

I am using this in a run.sh script to specify Thin:

rerun   -- thin start  --port=4567 -R config.ru

回答3:

As mentioned by iltempo and user2632580, the reason this fails is the list of servers Sinatra tries by default, failing on HTTP which the Mechanize gem has overriden.

An alternative approach to overcome this is to supply a different list of servers for Sinatra to try as per the documentation at http://www.sinatrarb.com/configuration.html (see "Built-in Settings" > ":server").

Example script:

require 'sinatra'
require 'mechanize'

set :server, %w[thin puma reel webrick]

get '/' do
   "Hello world!"
end

This list in the example is based on the current value of Sinatra::Base::server minus HTTP

来源：https://stackoverflow.com/questions/16777850/mechanize-sinatra-conflict

标签

ruby

sinatra

mechanize