簡(jiǎn)單的rackup配置

infinity = Proc.new {|env| [200, {"Content-Type" => "text/html"}, env.inspect]}
use Rack::CommonLogger
use Rack::ShowExceptions

map '/' do
  run infinity
end

map '/version' do
  map '/' do
    run Proc.new {|env| [200, {"Content-Type" => "text/html"}, "infinity 0.1"] }
  end

  map '/last' do
    run Proc.new {|env| [200, {"Content-Type" => "text/html"}, Rack::Request.new(env).params.inspect] }
  end
end

執(zhí)行先安裝rack gem install rack
使用 rackup -R infinity.ru -p 3000

其中map的寫法和routes.rb中做法差不多，回顧一下routes.rb中的寫法。

ActionController::Routing::Routes.draw do |map|
  map.connect ':controller/:action/:id'
end

routes.rb里面發(fā)生了什么呢？很不幸、里面過程錯(cuò)綜復(fù)雜，橫跨了至少四個(gè)類Builder,Mapper,Route,RouteSet，我只能告訴你結(jié)果，一句map.connect生成了一個(gè)Route對(duì)象。

rack代碼則簡(jiǎn)單的我可以輕易的討論。

module Rack
  ...

  class Builder
    def initialize(&block)
      @ins = []
      instance_eval(&block) if block_given?
    end

    ...
    def map(path, &block)
      if @ins.last.kind_of? Hash
        @ins.last[path] = self.class.new(&block).to_app
      else
        @ins << {}
        map(path, &block)
      end
    end

    def to_app
      @ins[-1] = Rack::URLMap.new(@ins.last)  if Hash === @ins.last
      inner_app = @ins.last
      @ins[0...-1].reverse.inject(inner_app) { |a, e| e.call(a) }
    end
    ...

  end
end

module Rack
  ...

  class URLMap
    def initialize(map)
      @mapping = map.map { |location, app|
        if location =~ %r{\Ahttps?://(.*?)(/.*)}
          host, location = $1, $2
        else
          host = nil
        end

        unless location[0] == ?/
          raise ArgumentError, "paths need to start with /"
        end
        location = location.chomp('/')

        [host, location, app]
      }.sort_by { |(h, l, a)| [-l.size, h.to_s.size] }  # Longest path first
    end

    ...
  end
end

注意[0...-1]是不包含-1這個(gè)元素的，所以to_app只執(zhí)行了前兩句。map最終生成了一個(gè)url和Rack::URLMap對(duì)象的Hash。而在rails當(dāng)中，url被切割成了多個(gè)segments。Rails這樣作也自有其用處，常見的redirect_to :action => 'action'就是這樣構(gòu)造出url的，但是對(duì)于輕量級(jí)應(yīng)用，就有一點(diǎn)大炮打蚊子了。
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