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module Rack
# Rack::Builder implements a small DSL to iteratively construct Rack
# applications.
#
# Example:
#
# require 'rack/lobster'
# app = Rack::Builder.new do
# use Rack::CommonLogger
# use Rack::ShowExceptions
# map "/lobster" do
# use Rack::Lint
# run Rack::Lobster.new
# end
# end
#
# run app
#
# Or
#
# app = Rack::Builder.app do
# use Rack::CommonLogger
# lambda { |env| [200, {'Content-Type' => 'text/plain'}, 'OK'] }
# end
#
# run app
#
# +use+ adds a middleware to the stack, +run+ dispatches to an application.
# You can use +map+ to construct a Rack::URLMap in a convenient way.
class Builder
def self.parse_file(config, opts = Server::Options.new)
options = {}
if config =~ /\.ru$/
cfgfile = ::File.read(config)
if cfgfile[/^#\\(.*)/] && opts
options = opts.parse! $1.split(/\s+/)
end
cfgfile.sub!(/^__END__\n.*/, '')
app = eval "Rack::Builder.new {\n" + cfgfile + "\n}.to_app",
TOPLEVEL_BINDING, config, 0
else
require config
app = Object.const_get(::File.basename(config, '.rb').capitalize)
end
return app, options
end
def initialize(&block)
@ins = []
instance_eval(&block) if block_given?
end
def self.app(&block)
self.new(&block).to_app
end
# Specifies a middleware to use in a stack.
#
# class Middleware
# def initialize(app)
# @app = app
# end
#
# def call(env)
# env["rack.some_header"] = "setting an example"
# @app.call(env)
# end
# end
#
# use Middleware
# run lambda { |env| [200, { "Content-Type => "text/plain" }, ["OK"]] }
#
# All requests through to this application will first be processed by the middleware class.
# The +call+ method in this example sets an additional environment key which then can be
# referenced in the application if required.
def use(middleware, *args, &block)
@ins << lambda { |app| middleware.new(app, *args, &block) }
end
# Takes an argument that is an object that responds to #call and returns a Rack response.
# The simplest form of this is a lambda object:
#
# run lambda { |env| [200, { "Content-Type" => "text/plain" }, ["OK"]] }
#
# However this could also be a class:
#
# class Heartbeat
# def self.call(env)
# [200, { "Content-Type" => "text/plain" }, ["OK"]]
# end
# end
#
# run Heartbeat
def run(app)
@ins << app #lambda { |nothing| app }
end
# Creates a route within the application.
#
# Rack::Builder.app do
# map '/' do
# run Heartbeat
# end
# end
#
# The +use+ method can also be used here to specify middleware to run under a specific path:
#
# Rack::Builder.app do
# map '/' do
# use Middleware
# run Heartbeat
# end
# end
#
# This example includes a piece of middleware which will run before requests hit +Heartbeat+.
#
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
def call(env)
to_app.call(env)
end
end
end
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