#rails 3

[bionuc-blog]

request.xhr? in Rails 3

In Rails 3, you shouldn’t rely on request.xhr? to know if request is done via AJAX or not because this is not a method that returns true or false but a predicate function that returns the index of the first match so this can return 0 which will lead to false in any check

To overcome this, always use !!request.xhr? to do the check

[nickmalcolm]

Running Rails 3 commands on a Rails 2 box

I was at home last night trying to administer my new website Lost Lookout when I ran into some trouble. I'm using my work's server (thanks guys!) to host my web app.

The box is, by default, using Rails version 2. My app is Rails version 3. So, when you fire up the terminal/console, you enter something like:

$ RAILS_ENV=production rails console

It acts like rails 2 and makes  new project called console. >(

Super lame.

I spent ages trying to Google the correct command to make it run as if it's Rails 3. I had it written down at work. Now I'm at work I want to tell the world and myself, for future reference, how to do it:

$ RAILS_ENV=production bundle exec rails console

That simple little bundle exec. It makes the command run in the context of the bundle. Which, for my project, is Rails 3. Voila!

[developrubyonrails]

Problems faced while setting up Rails 3 with ruby-1.9.2

I migrated all my applications to Rails 3 with ruby 1.9.2,  After I installed ruby I faced few errors. Few of them are

1) The arrow keys were not working in irb console and “no such file to load –readline” error. This is the problem which occurs when the readline extension is not installed with ruby source. All you have to do to fix this error is,

Go to your ruby source folder you downloaded and installed ruby from.

1.  cd  ~/ruby-1.9.2 2.  cd  ext/readline and execute the commands below. 3. ruby  extconf.rb 4. make 5. sudo make install If you find any errors while executing ruby extconf.rb showing ..no for each checkings. Then you need to install these two libraries on your system sudo apt-get install libncurses5-dev libreadline5-dev then later execute the commands starting from 3. 2) The other error was after I create application and start the server, the error was “no such file to load –openssl” Again it was the error with openssl ruby extension not installed with ruby, you can fix this error by executing the following commands.

Go to the ruby source file 1. cd  ~/ruby-1.9.2 2. cd  ext/openssl and execute the commands below. 3. ruby extconf.rb 4. make 5. sudo make install

If you find any errors while executing the command ruby extconf.rb showing ..no for each checkings, then you need to install the package in your system sudo apt-get install openssl libopenssl-ruby libssl-dev then later execute the commands starting from 3. Similarly I found may other files which were causing errors since the extensions were not installed like zlib etc.. If you find ‘no such file to load error ‘ for any of the extensions, then you need to go to ruby source folder. Go to respective directory inside ext/ (eg: readline/ for ‘no such file to load –readline’) and execute the following commands inside that folder ruby extconf.rb make sudo make install If you cannot successfully execute ruby extconf.rb, then you need to install respective libraries and execute these commands above again.

Note: I work on ubuntu operating system, If you face same errors in centos or any servers which I faced on a server with CentOS where you don’t have apt-get or aptitude installer, you need to search for particular package with yum search and install the package compatible with your operating system. Hope this helps.

Install Rails3 on Ubuntu system with Rails 2.X.X in the system.

I was working on Rails 2.x.x and all I did to catch Rails3 was removed the old Ruby library, un-installed Rails and gems and installed a latest Ruby library which supports Rails3. The commands I executed to remove the Ruby library were # sudo gem uninstall rails This will uninstall the Rails in your Ubuntu system # sudo apt-get purge ruby rubygems  This will purge the Ruby library and all gems installed in your system. After un-installing I installed Ruby-1.9.2 by following commands # wget ftp://ftp.ruby-lang.org//pub/ruby/1.9/ruby-1.9.2-p0.tar.gz # tar -xvvf ruby-1.9.2-p0.tar.gz # cd ruby-1.9.2 # ./configure # make # sudo make install It was just installation of this Ruby library, it got me the irb and gem installed in my system since all Ruby libraries with 1.9.X versions has irb and gem inbuilt unlike old Ruby versions where we had to install irb and gem manually. I installed Rails3 with following command # sudo gem install rails –version 3.0.0 # sudo bundle install      // This installs all the supportive bundles required. This got me Rails3 installed in my system, and creation of project and running the application server is little different compared to Rails 2.x.x . Creating sample application using Rails3 with scaffolding ->     rails new application_name -d mysql ->     rails generate scaffold Post title:string body:text ->     rake db:create   ->     rake db:migrate ->     rails server I got the welcome page of Rails3 app.

Source: RailsCarma.com

[aawaara]

How to get created_at timestamp from mongo BSON id using mongoid

Writing this down as I always forget this, and this search query is not very google friendly either (and I usually waste a lot of time looking for this, and probably so would others). This is how you do it:

sample_object.id.generation_time

Now the bonus stuff! If you wan to do range queries for created_at timestamp on the BSON id, this is how you do it:

https://gist.github.com/amitsaxena/6977506

[tree-sitter]

[aawaara]

Rails 3: Custom validation messages for the same column name using some other column value

Problem: We wanted to add custom validation message, and call the same mysql table column with different names depending on the value of some other field. After much googling I couldn’t find any suitable answers. Posting the solution I came up with, so that it can be of help to others:

Solution: 

I couldn’t find solutions using procs, interpolations, etc. I wrote a custom validator, as all the columns are available there. Below is the sample code:

https://gist.github.com/4286604

Please note that linktype and url are columns in the links table.

Also answered a related question on Stackoverflow here:

http://stackoverflow.com/questions/5085284/how-can-i-interpolate-ivars-into-rails-i18n-strings-during-validation/13881719#13881719

[aakashd-problem]

Access Rails routes helpers outside the controllers e.g. in Models

Problem: The routes helper methods are available in views and controller as they are most of the time needed for displaying links in views or redirecting to other paths. But in one case I was expiring a page cache on an after_create callback of a model, for which I needed to access the path generated for that controller#action.

Solution: The RoutSet instance which contains all the helper methods is part of the Rails::Application object, and can be accessed at Rails.application.routes. You can access any URL helpers as follows:

  Rails.application.routes.url_helpers.notification_path(notification) Rails.application.routes.url_helpers.notifications_path 

[29stepz-blog]

Rails 3 convert superclass to subclass

In a recent rails 3.0 project I was working on I had an interesting dilemma. I have two models, User and Member. Member is a subclass of User.

Now when a user logs into the system the system checks what roles and permissions each user has and then redirects them accordingly. e.g. if the user record has a role of 'Member' then we redirect them to the member section.

Now since Member is a subclass of User, we are using STI ( Single table inheritance ) within rails whereby all the member attributes are stored as columns within the single user table. Member has an additional method called active? which determines if the membership level is active or not. However, in the logic which checks where to redirect signins because only User objects are returned, each call to active? is made on the superclass of User and not Member. To fix this I could redefine active? within the User model but it means duplication of the active? method inside Members class.

Another alternative would be to convert the User model into a Member object. ActiveRecord instances have a method called becomes(klass) which takes the name of the class to convert to. The definition of becomes from the API docs as follows:

Returns an instance of the specified klass with the attributes of the current record. This is mostly useful in relation to single-table inheritance structures where you want a subclass to appear as the superclass.

Full link of the api can be found here: http://api.rubyonrails.org/classes/ActiveRecord/Persistence.html#method-i-becomes

Now we are going the other way round from superclass to subclass which is unorthodox but works in my case here. An example of what I ended up with: