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https://github.com/steveklabnik/frp_shoes

Functional Reactive Programming + Shoes
https://github.com/steveklabnik/frp_shoes

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Functional Reactive Programming + Shoes

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README 

        
FRP Shoes

=========



Functional reactive programming with Shoooooooes.



Reference Implementation

------------------------



`reference.rb` contains a simple Shoes app, written in the usual Shoes style.

Basically, there are two buttons, +1 and -1, and a `para` with a count. It

starts at zero, and the buttons increment and decrement the count.



FRP Implementation

------------------

`frp.rb` contains the same app, but written in an FRP style with [frappuccino](https://github.com/steveklabnik/frappuccino).



What's different?

-----------------



Here's the diff:



```diff

--- reference.rb	2013-04-23 12:05:50.000000000 +0200

+++ frp.rb	2013-04-23 15:01:17.000000000 +0200

@@ -1,19 +1,40 @@

+require 'frappuccino'

+

+class Button

+  def initialize(event)

+    @event = event

+  end

+

+  def push

+    emit(@event)

+  end

+end

+

 Shoes.app :height => 150, :width => 250 do

   background rgb(240, 250, 208)



+  @plus = Button.new(:+)

+  @minus = Button.new(:-)

+

+  @stream = Frappuccino::Stream.new(@plus, @minus)

+

+  @counter = @stream

+              .map_stream(:+ => 1, :- => -1, :default => 0)

+              .inject(0) {|sum, n| sum + n }

+

   stack :margin => 10 do

     button "+1" do

-      @count += 1

-      @label.replace "Current count: #@count"

+      @plus.push

     end



     button "-1" do

-      @count -= 1

-      @label.replace "Current count: #@count"

+      @minus.push

     end



-    @count = 0

+    @label = para "Current count: #{@counter.to_i}"



-    @label = para "Current count: #@count"

+    @counter.on_value do |value|

+      @label.replace "Current count: #{value}"

+    end

   end

 end

```



Let's go over the differences:



The old buttons used to handle both incrementing the count, as well as

replacing the label. Now, the buttons do one thing: call a method on their

`Button` reference. The streams handle responding to the press and doing

the update.



We have that `Button` classes. This is largely because of the way that

Shoes works; I _think_ I could get away from this, but in larger GUI apps

you'll have pure Ruby models anyway; putting logic into the UI stuff is

a general antipattern. It's nice for small things, which is one of the things

Shoes is great at, but bigger apps (like Hackety) get out of control really

quickly.



Constructing the count is no longer split between the two buttons, it's in the

`#inject` call. This is a win: it went from being spread out among two places

to being in just one place.



The update is now handled in one place as well: the `#on_value` callback we've

added to the stream. Same deal: this was in two places, now it's in one.



That's really it. Neat.



Running this yourself

---------------------



Okay, so I really wanted to make this mega-easy, so I included a

Gemfile... the issue is that Shoes 4 is still in flux, and so it

doesn't include binaries in the gem. Nuts. So, you'll have to

clone down Shoes, and then run it from there. 



Don't forget: Shoes 4 is based on JRuby, so you have to be

using that.



Anyway, here's what you have to do:



```bash

$ git clone https://github.com/shoes/shoes4.git

$ git clone https://github.com/steveklabnik/frappuccino.git

$ git clone https://github.com/steveklabnik/frp_shoes.git

$ cd frappuccino

$ bundle

$ rake install

$ cd ../shoes4

$ bundle

$ bin/swt-shoooes ../frp_shoes/frp.rb

```