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Getting started with Ruby and Sinatra

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I’ve been doing a little work with Ruby, starting with some XHTML parsing with Nokogiri. I’ve just created my first web page using Sinatra.

While the instructions makes it look simple, it was a little more complex due a package dependency error.

Installation

$ sudo gem install sinatra
Password:
Successfully installed rack-1.2.1
Successfully installed sinatra-1.0
2 gems installed
Installing ri documentation for rack-1.2.1...
Installing ri documentation for sinatra-1.0...
Installing RDoc documentation for rack-1.2.1...
Installing RDoc documentation for sinatra-1.0...

Smoking it

Following the 5 line example on the home page, didn’t produce the result I expected.

 ruby rb42.rb
/Library/Ruby/Gems/1.8/gems/rack-1.2.1/lib/rack/utils.rb:138:in `union': can't convert Array into String (TypeError)
	from /Library/Ruby/Gems/1.8/gems/rack-1.2.1/lib/rack/utils.rb:138
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
	from /Library/Ruby/Gems/1.8/gems/rack-1.2.1/lib/rack/request.rb:1
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
	from /Library/Ruby/Gems/1.8/gems/rack-1.2.1/lib/rack/showexceptions.rb:3
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
	 ... 7 levels...
	from /Library/Ruby/Gems/1.8/gems/sinatra-1.0/lib/sinatra.rb:4
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:36:in `require'
	from rb42.rb:2

Some Googling found a reference to a compatibility problem. While the syntax given on the post wasn’t correct, it was sufficient for me to find a correct solution.

$  sudo gem uninstall rack
Remove executables:
	rackup

in addition to the gem? [Yn]  y
Removing rackup

You have requested to uninstall the gem:
	rack-1.2.1
sinatra-1.0 depends on [rack (>= 1.0)]
If you remove this gems, one or more dependencies will not be met.
Continue with Uninstall? [Yn]  y
Successfully uninstalled rack-1.2.1

$ sudo gem install rack --version '1.2.0'
Successfully installed rack-1.2.0
1 gem installed
Installing ri documentation for rack-1.2.0...
Installing RDoc documentation for rack-1.2.0...

And now expected results starting then viewing http://localhost:4567/

$ ruby rb42.rb
== Sinatra/1.0 has taken the stage on 4567 for development with backup from Mongrel

Environment

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.5.8
BuildVersion:	9L31a
$ ruby --version
ruby 1.8.6 (2009-06-08 patchlevel 369) [universal-darwin9.0]
$ gem --version
1.3.6