Based off of functional reactive programming, oscillo gives you a signal that represents a value changing over time. You can manipulate signals and combine them together in various ways.


Add this line to your application's Gemfile:

gem 'oscillo'

And then execute:

$ bundle

Or install it yourself as:

$ gem install oscillo


Creating and using signals

Creating a signal is as simple as

s = Oscillo::Signal.new

You modify the value of the signal with s << :value and you get the current value of the signal with s.value, or s.val if you want to save a couple of letters.

If you want to give a signal a starting value, you just pass it to the constructor.

s = Oscillo::Signal.new(0)

Following other signals

If you pass another signal as an argument to new, the signal's value will follow the other one.

a = Oscillo::Signal.new
b = Oscillo::Signal.new(a)

a << :value
b.val #=> :value

You can pass a block to new to modify how the new signal follows the old.

a = Oscillo::Signal.new(0)
b = Oscillo::Signal.new(a) { |v| v * 2 }

a << 3
b.val #=> 6

You can also follow multiple signals at once. The new signal will change if any of the signal that you follow changes.

a = Oscillo::Signal.new(0)
b = Oscillo::Signal.new(0)
c = Oscillo::Signal.new(a, b) { |v1, v2| v1 + v2 }

a << 2
c.val #=> 2
b << 3
c.val #=> 5

Reacting to signal changes

Eventually, you want to perform some action when the value of the signal changes. To do this, register a callback with the #on_change method. You can also use #each if you want to think of it as an Enumerable.

s = Oscillo::Signal.new
s.on_change { |v| puts "The new value is: #{v}" }
s << 1
#=> "The new value is: 1

Useful methods in the block

The last argument given to the block passed to new is the signal itself. This is so you utilize other methods to query the signal and modify it's changed value.

Oscillo::Signal#abort aborts the new value change, keeping the old one.

a = Oscillo::Signal.new
b = Oscillo::Signal.new(a) { |v, s| s.abort if v == :bad; v }

a << :good
b.val #=> :good
a << :bad
b.val #=> :bad

Oscillo::Signal#source gives the original signal that caused the cascade of changes. This is useful if you are following multiple signals and want to know which one actually changed.

a = Oscillo::Signal.new
b = Oscillo::Signal.new
c = Oscillo::Signal.new(a, b) do |v1, v2, s|
  "The last change was to #{s.source.val}"

a << 1
c.val #=> "The last change was to 1"
b << 2
c.val #=> "The last change was to 2"

Combining signals

You can combine signals together in different ways. For example, Oscillo::Combine.either updates the new signal to the value of whichever was the last signal to change.

a = Oscillo::Signal.new
b = Oscillo::Signal.new
c = Oscillo::Combine.either(a, b)
a << "a changed"
c.val #=> "a changed"
b << "b changed"
c.val #=> "b changed"

See Oscillo::Combine for all combination methods.


A signal can thought of a sequence of values over time. Therefore, Oscillo::Signal implements a large number of Enumerable's methods. For example,

a = Oscillo::Signal.new(0)
b = a.map { |v| v ** 2 }
a << 3
b.val #=> 9

See Oscillo::Enumerable for all the methods implemented.


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request