Category Archives: Ruby

Using named gemsets with rvm

Posted on by
Reply

Problem

You want to be able to use different gems/rails version for your application after installing the latest rails version, without having to use bundle exec.

 

Solution

You can use the named gemsets with rvm.

More instructions are here: http://beginrescueend.com/gemsets/basics/

so you can install two gemsets for example ruby-1.9.3-p0@rails3_0_11 and another with ruby-1.9.3-p0@rails3_2_1

you could then do :

rvm gemset create rails3_0_11 rails3_2_1

rvm 1.9.3-p0@rails3_0_11
gem install rails -v 3.0.11

rvm 1.9.3-p0@rails3_2_1
gem install rails -v 3.2.1

rvm gemset use rails3_0_11
bundle install

you could then also use some aliases in your ~/.bashrc file to be able to use the gemsets by using only one command as for example in ($ rvm3011):

# Rails 3.0.x
alias rvm3011="rvm gemset use rails3_0_11"
alias rvm3012="rvm gemset use rails3_0_12"

# Rails 3.2.x
alias rvm321="rvm gemset use rails3_2_1"
alias rvm322="rvm gemset use rails3_2_2"

Cucumber – Carrierwave – ImageUploader – Variable class

Posted on by
Reply

Problem
You would like to test the carrierwave imageuploader with a cucumber test, but you would also like to use a generic step that can be used with different classes and different image file column names.

Solution
Use the following and perhaps put it a file named features/common_steps.rb

Then /^the url for the column "([^"]*)" of model "([^"]*)" should be "([^"]*)"$/ do |col,mdl,url|
  # First get tne class name from the mdl argument by using the Kernel.const_get method
  m = Kernel.const_get(mdl).first
  # And then use the send with the column name (col) to call the model's field,
  # the url method of ImageUploader to get the full path
  # and basename to get only the file name
  File.basename(m.send(col).url).should == url
end

ActiveSupport::TimeWithZone comparisons

Posted on by
Reply

Problem
You have two dates that you want to compare in your Rails application, which are both ActiveSupport::TimeWithZone.

Although they both look identical, when you are trying to compare them for equality (using ==), you get back false as a result.

 

Solution

These dates can have a difference in milliseconds that doesn’t normally get displayed. So first of all try to use to_f to see if they really have a difference.

If they do, then you would need to compare them by converting them to integers first as in :

date_a.to_i == date_b.to_i

and you should be getting back true

Secure Random passwords in Ruby

Posted on by
Reply

Problem
You would like to use a random password in ruby. Most solutions describe using the Digest library (Digest::SHA1).

Solution
According to the post here, you can achieve the same by using ActiveSupport’s secure_random library.
To use it in Ruby outside Rails use:

require 'active_support/secure_random'
ActiveSupport::SecureRandom.hex(10)
ActiveSupport::SecureRandom.base64(10)


and inside rails:

SecureRandom.hex(10)