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Problem
When using the god gem in a Rails 2.3.2 application, when you unpack (freeze) the god gem with :

sudo rake gems:unpack

it creates the god drectory in vendor/gems with root owner, and group permissions.

Solution
Remember to change owner and group for the folder

sudo chown -R user_name vendor/gems/god-0.11.0
sudo chown -R user_name vendor/gems/god-0.11.0

Problem
Cannot install RMagick as there is an error about nob being able to find some shared libraries.

Solution
After reading the RMagick installation FAQ it seem there is a problem with the LD_LIBRARY_PATH that cannot find the needed libraries as they are installed in /usr/local/lib instead of /usr/lib.
Doing a quick search revealed that people suggest that the LD_LIBRARY_PATH shouldn’t be changed, for various reasons.
So, the quick solution is to create a couple of symbolic links for the libraries that cannot be found, ie:

sudo ln -s /usr/local/lib/libMagickWand.so.4 /usr/lib/libMagickWand.so.4
ln -s /usr/local/lib/libMagickCore.so.4 /usr/lib/libMagickCore.so.4

Problem
You want to use find in Rails for a case sensitive search. For example in your authentication logic you have something to find the user to login as in:
u=User.find_by_login(‘username’)
If you don’t want to limit the available logins with case insensitive validation in the model, then the above code will not work if you have ‘Username’ and ‘username’ as available logins, as the find will only return one of them.

Solution
Change the find method to use the BINARY keyword in your database (only used with MySQL), as in the following:
u=User.find(:first, :conditions => ["BINARY login = ?", login])

Problem
You get a ’406 Not Acceptable’ response from the web server when you try to use the princely plugin for generating pdf on a Ruby on Rails application hosted on dreamhost.

Solution
Having tried the ‘Extra Web Security’ settings in dreamhost Web panel, and setting them on/off did not get very far.
Also setting up an .htaccess file didn’t seem to make any difference.
So the mod_security settings did not seem to be the cause of the problem.
Having a look at the apache error log files which in the case of the dreamhost ps are in /usr/local/dh/apache2/logs/apache2-ps_name it turns out that the problem was that the path for the prince binary was not setting up correctly in the file vendor/plugins/princely/lib/prince.rb on line 26.
A quick hack to make it work until finding the reason for the problem is to hardcode the path to the prince binary, so:
@exe_path = `which prince`.chomp
if @exe_path.nil?
@exe_path=’/usr/local/bin/prince’
end

Problem
You have the error showing up after starting either the server (./script/server) or the console (./script/console).
For my particular case it started appearing after installing the Rails 3.0 beta3 version, and in an application developed with Rails 2.3.2.

Solution
Just install the system_timer gem:
sudo gem install system_timer

Problem
When you get the above error you cannot login to your application.

Solution
You will need to delete the cookies for the authentication, so in Firefox (Linux) go to Preferences, remove individual cookies for the specific domain.

Problem
You have just deployed your rails application to dreamhost but you are getting this error from passenger.

Solution
There was a change in the ImageMagic between versions 6.4.3 and 6.4.4 from the affinity function to remap.
If you don’t want, or don’t have time to recompile the ImageMagick and install the rmagick gem, you can comment out the two declarations for the alias functions, located around lines 782 and 1525 in the file rmagick-2.12.2/lib/RMagick.rb:

alias_method :affinity, :remap

Problem
You want to deploy to a shared host (dreamhost) that has a later version of rails from the one you have developed your application.
You also have a later version installed in your development pc,and using rake rails:freeze:gems uses the latest one and not the one you want.

Solution
Use the following to freeze the specific version you want, and by using your gems you have installed:
rake rails:freeze:gems VERSION=2.3.2

Problem
You have a list, usually after using join(“,”) in an array that consists of different values ie “one, two, three, four”, but you want to replace the last comma with and so it would be “one, two, three and four”.

Solution
Use reverse initially to reverse the string, then use sub to replace the last comma with the word and reversed (dna), and then finally reverse the string again.

string_with_and=string_with_commas.reverse.sub(/,/, ‘ dna ‘).reverse

or, thanks to Akhil's comment, for Arrays in Rails we can use the to_sentence method as in:

string_with_no_commas=array.to_sentence(options = {:last_word_connector => ” and “})

Problem
Trying to use the rake task for populating latitude and longitude details for addresses as described in the Web mashup projects book, gives the error about attempting to call private method.

Solution
Use the method save instead of update as suggested in the book.