sudo gem update –system

(Those are two dashes and not just one, in cause your browser displays them as one.)

There you go.

respond_to do |format|
  format.xml { render :xml => @users.to_xml
end

The above will create and return fully functional XML which is all good and dandy.

Well, it’s not. The above will mirror each and every detail about your users table in your database. But what if you don’t want to include the user passwords in the XML? What if you want to rename one of the fields to something else in your XML?

You use the Builder. With the help of the Builder, you can modify the XML to look like anything you want and not just mirror your table structure completely. Here is how you use the Builder:

xml = Builder::XmlMarkup.new
xml.instruct!
xml.users do
  @users.each { |user|
    xml.username user.username
    xml.email user.email_address
    xml.write-whatever-you-want-here user.whichever-field-you-need
  }
end

respond_to do |format|
  format.xml { render :xml => xml.target! }
end

The above code creates a new Builder object, then defines for a set of users to be shown in the XML. Then, the @users array is processed, and inside each user node in the XML you’re pretty much able to do whatever you want – including calling other methods you might need on-the-fly.

So whenever you need just a tad bit more freedom when working with XML, discard the .to_xml approach and create your own Builder object. That works like a charm!

If you want to keep everything to one encoding, you could make use of Iconv.conv(‘UTF-8′, <whatever encoding>, string) to convert the data from the input field to UTF-8. But to make the iconv() wrapper work properly, it needs to know what to convert from… So how do you acquire this knowledge?

Try to use the Ruby gem rchardet by Jeff Hodges. Here is an example of how to use it:

require ‘rchardet’

[...]

cd = CharDet.detect(params[:my_upload_form][:uploaded_file])
encoding = cd['encoding']

converted_string = Iconv.conv(‘UTF-8′, encoding, params[:my_upload_form][:uploaded_file])

The above is not bullet proof, but it’ll get you going. If you have alternative ideas in this regard, please comment to let us all know.

ERROR: cannot drop the currently open database

This is because you are trying to delete the database that you are currently connected to (or in MySQL jargon: the database you are current USEing). To fix the problem, try to issue the following command:

\connect postgres

This will connect you to the postgres database in PostgreSQL, sometimes referred to as the maintenance database. From here, try to issue your drop command again – it will now work out for you as expected.

Say you want to copy a file from the remote server to your own computer, a file called my_file.txt. In this case, you would issue the following command in your terminal:

scp your_login@addres.of.remote.server:my_file.txt .

This makes your computer connect to the server with the login you provide, and copy the my_file.txt file to the directory you are currently working (using the exact same file name locally on your computer, that’s why there is a dot in the end of the command).

uninitialized constant Gem::GemRunner (NameError)

If you get the above when trying to use gem, first of all, you need to find out which gem you’re using. Open up your shell and type in the following:

which gem

This will print out which gem you’re using and the location of it, typically being /usr/bin/gem or /usr/local/bin/gem.

Next, open up the actual gem file in your favourite text editor. If you’re using TextMate for Mac OS X, this can be accomplished directly from your shell by issuing the mate /usr/bin/gem command (you might need to change the path to gem to reflect your system setup).

Here, you’ll see a line reading require ‘rubygems’. Just below this line, add require ‘rubygems/gem_runner’, save the file and try to use gem again. It should work fine now. The change you need to do is shown below:

This showns the gem file brought up in TextMate. Line 10 is the fix.

You might have tried to save the vCard as ISO-8859-1, UTF-8 or the likes, and it still doesn’t work in Address Book. You might even have tried to add charset info in the MIME type of the vCard, having it display something like text/vcard; charset=iso-8859-1 all the while it still doesn’t work. Bugger.

The only solution is to make Address Book use a different character encoding for the vCards. If you access Address Book -> Settings… -> vCard, you’ll see the ability to change the character encoding. However, Address Book might have chosen vCard version 3.0 for you per default. Change this to 2.1, then change the character set to e.g. Windows Latin 1, and then change the version back to version 3.0.

Having done the above, the import of vCards containing foreign characters will work as expected. This includes vCards exported from Meeho!™.

A screenshot of the settings regarding vCards in Address Book.

(One last note: Having to choose vCard version 2.1 to change the character encoding, then changing the version back to 3.0 AND having Address Book preserve the encoding settings might be a bug… Seems odd that it preserves the encoding settings while jumping from version 2.1 to version 3.0, when the dropdown menu is dimmed when set to vCard version 3.0, indicating that a change is not possible in that case…)

sudo gem environment

This will give you an overview of the environment settings for RubyGems. Find the “GEM PATHS” settings and there you go:

A screenshot of my l33t Terminal.app.

class MyController < ApplicationController
layout ‘main’

 def my_method

   # Do stuff here…
   render :layout => ‘my_layout’

 end

end