Merge branch 'new_recipes'

Author: thirdtruck

chapters/design_patterns/command.md

@@ -0,0 +1,59 @@
+---
+layout: recipe
+title: Command Pattern
+chapter: Design Patterns
+---
+## Problem
+
+You need to let another object handle when your private code is executed.
+
+## Solution
+
+Use the [Command pattern](http://en.wikipedia.org/wiki/Command_pattern) to pass along references to your functions.
+
+{% highlight coffeescript %}
+# Using a private variable to simulate external scripts or modules
+incrementers = (() ->
+	privateVar = 0
+
+	singleIncrementer = () ->
+		privateVar += 1
+
+	doubleIncrementer = () ->
+		privateVar += 2
+	
+	commands = 
+		single: singleIncrementer
+		double: doubleIncrementer
+		value: -> privateVar
+)()
+
+class RunsAll
+	constructor: (@commands...) ->
+	run: -> command() for command in @commands
+
+runner = new RunsAll(incrementers.single, incrementers.double, incrementers.single, incrementers.double)
+runner.run()
+incrementers.value() # => 6
+{% endhighlight %}
+
+## Discussion
+
+With functions as first-class objects and with the function-bound variable scope inherited from Javascript, the CoffeeScript language makes the pattern nearly invisible.  In fact, any function passed along as callbacks can act as a *Command*.
+
+The `jqXHR` object returned by jQuery AJAX methods uses this pattern.
+
+{% highlight coffeescript %}
+jqxhr = $.ajax
+	url: "/"
+
+logMessages = ""
+
+jqxhr.success -> logMessages += "Success!\n"
+jqxhr.error -> logMessages += "Error!\n"
+jqxhr.complete -> logMessages += "Completed!\n"
+
+# On a valid AJAX request:
+# logMessages == "Success!\nCompleted!\n"
+{% endhighlight %}
+

wanted-recipes.md

@@ -109,7 +109,6 @@ foo 1, 2, 3
 
 * Behavioral Patterns
   * Chain of Responsibility
-  * Command
   * Iterator
   * Mediator
   * Observer