Ruby – Problem installing sqlite3-ruby!

Ruby uses the case expression instead.

case x
when 1..5
  "It's between 1 and 5"
when 6
  "It's 6"
when "foo", "bar"
  "It's either foo or bar"
when String
  "You passed a string"
else
  "You gave me #{x} -- I have no idea what to do with that."
end

Ruby compares the object in the when clause with the object in the case clause using the === operator. For example, 1..5 === x, and not x === 1..5.

This allows for sophisticated when clauses as seen above. Ranges, classes and all sorts of things can be tested for rather than just equality.

Unlike switch statements in many other languages, Ruby’s case does not have fall-through, so there is no need to end each when with a break. You can also specify multiple matches in a single when clause like when "foo", "bar".

My problem was slightly different, and in fact non of the solutions I found on-line worked.

When trying to install sqlite3-ruby after upgrading to Snow Leopard and XCode 4.0 trial, I got the message

checking for sqlite3.h... yes
checking for sqlite3_libversion_number() in -lsqlite3... no
sqlite3 is missing. Try 'port install sqlite3 +universal' or 'yum install sqlite3-devel'

however sqlite3 was installed, and also re-installing did not help. I already had the troub le before with 64-bit and universal versions, but that I had cleared as well. In fact, I could work with sqlite3.

So gem install should also tell you something along these lines:

Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/sqlite3-ruby-1.3.1 for inspection.

So cd to that directory and there look for extconf.rb, mine was in ./ext/sqlite3/extconf.rb I found that ruby was checking for the the sqlite3 library using

asplode('sqlite3') unless find_library 'sqlite3', 'sqlite3_libversion_number'

So I fired up irb and checked why this didn't work:

  require 'mkmf'
   find_library 'sqlite3', 'sqlite3_libversion_number'

Well, in fact this works and my ruby find the library. So why doesn't it work from the setup? Inspecting extconf.rb closely showed the following line:

  sqlite = dir_config('sqlite3', ['/usr/local', '/opt/local', '/usr'])

When I execute this in irb:

require 'mkmf'
  sqlite = dir_config('sqlite3', ['/usr/local', '/opt/local', '/usr']) 
  find_library 'sqlite3', 'sqlite3_libversion_number'

I will surprisingly not find the library anymore. In fact I do not understand how this can be, but that's what happens.

So this is the cure: comment out the line

sqlite = dir_config('sqlite3', ['/usr/local', '/opt/local', '/usr'])

in extconf.rb

Then from /Library/Ruby/Gems/1.8/gems/sqlite3-ruby-1.3.1 I issued

 sudo ruby ./setup.rb

This went through with no problems (I tried before commenting out the sqlite= line, and it did not work)

Restarted the ruby application that had the problems with sqlite. Works fine.

Hope this will help someone.

Icecream