Random numbers in Ruby

Stop writing your own random string generators. Rails does this for you.

Warning: Because of (unclear) rounding issues and missing decimal places (see examples below),
do NOT use this when dealing with money. Use our amount helper instea...

$RANDOM on bash returns a random integer between 0 and 32767.

echo $RANDOM
9816
echo $RANDOM
30922

If you want to limit that to a certain maximum, you can just compare against the modulus of that maximum + 1. \
For example, the fo...

Sometimes you want to know exactly how many objects exist within your running Ruby process. Here is how:

stats = {}
ObjectSpace.each_object  {|o| stats[o.class].nil? ? stats[o.class] = 0 : stats[o.class] += 1 }; stats

=> {String=...

[1,2,3,4].sample
# => e.g. 4

If you'd like to cheat and give different weights to each element in the array, you can use the attached initializer to say:

[1,2,3,4].weighted_sample([1,1,1,1000])
# => probably 4

For my computer science bachelor's thesis I programmed and evaluated a CLI Test Case Prioritization (TCP) tool for makandra. It has been written as a Ruby Gem and was tested and evaluated against one Ruby on Rails project....

In Ruby 1.9, instance_eval calls the block the with receiver as the first argument:

• In Ruby 1.8, receiver.instance_eval(&block) calls block.call()
• In Ruby 1.9, receiver.instance_eval(&block) calls block.call(receiver)

This will blo...

The rubyforge gems model may not be perfect, but damnit people, when there’s a gem update I know that it has actually been tested somewhat and it’s not just whatever random point HEAD happens to be at, at that point in time, by some random Joe who...

I recently browsed through the ActiveSupport code and found some nice stuff I did not know about:

ActiveSupport::Callbacks

ActiveRecord-like callback...

While 2.0 will include a number of syntax changes, new features and general improvements, mentioned below, it is anticipated to remain backward compatible with code written for 1.9.3 and Matz has stated that the changes are less significant than t...