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Simple_admin met a Pieman November 7, 2008

Posted by dougmcinnes in Code, Plugins & Gems, Rails, Rake, Ruby.
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Simple_admin is a Ruby on Rails plugin I created at the Los Angeles Times that morphed into a collabrative effort between Dewey, Reid and myself as it traveled between projects and functionality was added.  I’ve just released it to our latimes github account: http://github.com/latimes/simple_admin/tree/master

The basic premise is to give a simple way of managing login usernames and passwords without a database.  The data is stored in a YAML file in the application with the passwords encrypted by String’s crypt() method.

To add users to the file there’s an included rake task: admin:add_user.  The username and password are passed as parameters:

rake admin:add_user username=mrwalrus password=mahbukkit

Rake will append the user to the login.yaml file or create a new one.  The default location for this file is config/admin/login.yml but can be overridden by setting the LOGIN_FILE environment variable in your application.  If you set the LOGIN_FILE differently in your different rails environment files you can have different usernames and passwords for development and production.

There’s also a rake task for adding multiple users at the same time from a text file list, giving them all random passwords.

To get the plugin to actually use Basic HTTP authentication to ask for usernames and passwords add this to your application controller:

include SimpleAdmin
before_filter :check_basic_http_credentials

Like all filters you can add conditions:

before_filter :check_basic_http_credentials, :only => :login

When including SimpleAdmin in your controller you also get access to the authenticate(username, password) method which can be used for custom login pages.  For example:

def login
  if authenticate(params[:username], params[:password])
    session[:admin] = true
    redirect_to main_page

Also included in the plugin is some code for marking different servers as “admin” servers and a way for a rails application to check to see if he’s an admin or not and change its behavior.  We used this on one application running on multiple boxes so we could turn off page caching on the admin-marked boxes so the administration WYSIWYG pages wouldn’t be cached and sent to non-admin users (that would be a big oops).

selectedIndex is your friend on IE6 November 5, 2008

Posted by reidmix in Code, Example, Javascript.
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While working on getting ChainedSelects to work on IE6, I realized there are multiple ways to set an option as selected.  Since ChainedSelects creates all the options for a pre-existing select, I first used the defaultSelected argument passed in the Option constructor:

option = new Option("name", "value", true);

Here, the third argument specifies whether the option is defaultSelected, when the select is first created or the form is reset. This worked fine in Firefox but IE6 blythely ignored it.  So I tried passing a fourth argument that specifies whether the option is currently selected.

option = new Option("name", "value", true, true);

Again, Firefox does the right thing but IE6 gets wacky and incosistently selects the correct option or sometimes does nothing at all.  It seems as if IE6 misses the “selected” message on the event queue, because it works only when i put some alert()s in there.

So I tried another way, by using the selected attribute after creating the option:

option = new Option("name", "value", true, true);
option.selected = true

Again, inconsistent behavior on IE6.  I went to the great oracle and asked google and tried setting the selected attribute to ‘selected’, ‘true’, and ‘yes’ all with no luck.  I wonder if this occurs because the select is pre-existing and is not newly created.  This led me to try out the selectedIndex attribute on the select element.

select = $('myselect')
select.selectedIndex = 3

Bingo!  This works in both Firefox and IE.  The index is 0-based as you would guess (0 is the first option is select.options).

Subselector, Moneypenny November 1, 2008

Posted by reidmix in ActiveRecord, Code, Database, Example, Monkey Patch, Plugins & Gems, Rails.
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Building on Josh and Damon‘s idea of Hacking a Subselect in ActiveRecord, I wondered if you could bake this kind of functionality into ActiveRecord.  So Doug and I went digging into the rails code, and came up with a plugin that adds subselects to ActiveRecord which we call Subselector.

So far, it only works on the Hash version of conditions.

On a column you wish to perform a subselect, pass a hash with :in, :not_in, :equals, or :not_equals as the only key.  The value is any of the options you normally would pass to ActiveRecord find.  Notice that we make sure to select a single column with the :select option:

Critic.find(:all, :conditions => { :id => {:in => {:select => :id, :conditions => {:active => true} } } })

Although the example may be contrived, here, we are looking for a critics that are in a set of active critics. The SQL:

select * from critics where id in (select id from critics where active = false)

You can see by default it runs the subselect on the table of outer select.  It gets more interesting you want to run a query on another ActiveRecord model:

Critic.find(:all, :conditions => { :id => {:in => {:model => :rankings, :select => :critic_id, :conditions =>
  {:week => 39} } } })

Here we set :model to :rankings.  Rankings is the ActiveRecord model to perform the find, notice we select the :critic_id column, the SQL is:

select * from critics where id in (select critic_id from rankings where week = 39)

And of course you can always just pass a string as a value to the subselect:

Critic.find(:all, :conditions => { :id => {:not_in => 'select id from critics where active = true' } })

Here’s how subselector can be used with the original example:

Post.find(:all, :conditions => :id => {:in => { :select => :post_id, :conditions => {:blog_id => self.id}, :order => "published_at DESC", :limit => options[:limit] || 10, :offset => options[:offset])} }, :order => "published_at DESC")

UPDATE: Subselector now likes Condition Arrays and Named Bind Variables.

Just pass the hash as a bind variable and specify the type (in/equals) of subselect in the string, make sure to enclose your ‘?’ inside parentheses:

Critic.find(:all, :conditions => ['id in (?)', {:select => :id, :conditions => 'active = true' }])
Critic.find(:all, :conditions => ['id not in (?)', {:select => :id, :conditions => {:active => false} }])
Critic.find(:all, :conditions => ['id in (?)', {:model => :rankings, :select => :critic_id, :conditions => {:week => 39} }])

As you can see, you can format the subselect hash just as above and can specify another model to run the subselect on. If you prefer to use named bind variable hashes, they still work (yay) as you would expect. And you can assign the subselect using them:

Critic.find(:all, :conditions => ['id in (:subselect)', {:subselect => {:select => :id, :conditions => {:active => false} } }])

UPDATE 2: Now with no ActiveRecord breakage

We’ve run the rails ActiveRecord tests without any problems. Let me know if you find any problems.