Wiretap

An iOS / OS X wrapper heavily inspired by ReactiveCocoa.

gem install motion-wiretap

Run the OSX specs using rake spec platform=osx

First things first

You MUST call cancel! on any wiretaps you create, otherwise they will live in memory forever. The upside is that you can create

Showdown

Open these side by side to see the comparison:

reactive.rb reactive.mm

Usage

These are taken from the specs.

Key-Value Observation

class Person
  attr_accessor :name
  attr_accessor :email
  attr_accessor :address
end

# listen for changes
person = Person.new
person.wiretap(:name) do |name|
  puts "name is now #{name}"
end
person.name = 'Joe'
# puts => "name is now Joe"

# bind the property of one object to the value of another
person_1 = Person.new
person_2 = Person.new
wiretap = person_1.wiretap(:name).bind_to(person_2.wiretap(:name))
person_2.name = 'Bob'
person_1.name # => "Bob"

# cancel a wiretap
wiretap.cancel!
person_2.name = 'Jane'
person_1.name
# => "BOB"

# bind the property of one object to the value of another, but change it using `map`
wiretap = person_1.wiretap(:name).bind_to(person_2.wiretap(:name).map { |value| value.upcase })
person_2.name = 'Bob'
person_1.name # => "BOB"

Working with arrays

# combine the values `name` and `email`
person = Person.new
[
  person.wiretap(:name),
  person.wiretap(:email),
].wiretap.combine do |name, email|
  puts "#{name} <#{email}>"
end

person.name = 'Kazuo'
# puts => "Kazuo <>"
person.email = 'kaz@example.com'
# puts => "Kazuo <kaz@example.com>"

# reduce/inject
person_1 = Person.new
person_2 = Person.new
[
  person_1.wiretap(:name),
  person_2.wiretap(:name),
].wiretap.reduce do |memo, name|
  memo ||= []
  memo + [name]
end
person_1.name = 'Mr. White'
person_1.name = 'Mr. Blue'
# => ['Mr. White', 'Mr. Blue']

# you can provide an initial 'memo' (default: nil)
[
  person_1.wiretap(:name),
  person_2.wiretap(:name),
].wiretap.reduce([]) do |memo, name|
  memo + [name]  # you should not change memo in place, the same one will be used on every change event
end

Monitoring jobs

# monitor for background job completion
-> {
  this_will_take_forever!
}.wiretap(Dispatch::Queue.concurrent) do
  puts "done!"
end

# Note: this is convenient shorthand for calling `queue`, `and_then`, and `start`
-> {}.wiretap.queue(...).and_then do ... end.start

# send a stream of values.  a lambda is passed in that will forward change
# events to the `listen` block
-> (on_change) do
  5.times do |count|
    on_change.call count
  end
end.wiretap.queue(Dispatch::Queue.concurrent).listen do |index|
  puts "...#{index}"
end.and_then do
  puts "done!"
end.start
# => puts "...0", "...1", "...2", "...3", "...4", "done!"

Let's do something practical!

# bind the `enabled` property to the Wiretap object to a check on whether
# `username_field.text` and `password_field.text` are blank
@login_button.wiretap(:enabled).bind_to(
  [
    @username_field.wiretap(:text),
    @password_field.wiretap(:text),
  ].wiretap.combine do |username, password|
    username && username.length > 0 && password && password.length > 0
  end
  )

Notifications

notification = "NotificationName".wiretap do
  puts "notification received!"
end

# rememder: it's *important* to cancel all wiretaps!
notification.cancel!