Merge branch 'bridge_pattern' into memento_pattern

Author: thirdtruck

chapters/design_patterns/bridge.textile

@@ -0,0 +1,55 @@
+---
+layout: recipe
+title: Bridge Pattern
+chapter: Design Patterns
+---
+
+h2. Problem
+
+You need to maintain a reliable interface for code that can change frequently or change between multiple implementations.
+
+h2. Solution
+
+Use the Bridge pattern as an intermediate between the different implementations and the rest of the code.
+
+Assume that you developed an in-browser text editor that saves to the cloud.  Now, however, you need to port it to a stand-alone client that saves locally.
+
+{% highlight coffeescript %}
+class TextSaver
+	constructor: (@filename, @options) ->
+	save: (data) ->
+
+class CloudSaver extends TextSaver
+	constructor: (@filename, @options) ->
+		super @filename, @options
+	save: (data) ->
+		# Assuming jQuery
+		# Note the fat arrows
+		$( =>
+			$.post "#{@options.url}/#{@filename}", data, =>
+				alert "Saved '#{data}' to #{@filename} at #{@options.url}."
+		)
+
+class FileSaver extends TextSaver
+	constructor: (@filename, @options) ->
+		super @filename, @options
+		@fs = require 'fs'
+	save: (data) ->
+		@fs.writeFile @filename, data, (err) => # Note the fat arrow
+			if err? then console.log err
+			else console.log "Saved '#{data}' to #{@filename} in #{@options.directory}."
+
+filename = "temp.txt"
+data = "Example data"
+
+saver = if window?
+	new CloudSaver filename, url: 'http://localhost' # => Saved "Example data" to temp.txt at http://localhost
+else if root?
+	new FileSaver filename, directory: './' # => Saved "Example data" to temp.txt in ./
+
+saver.save data
+{% endhighlight %}
+
+h2. Discussion
+
+The Bridge pattern helps you to move the implementation-specific code out of sight so that you can focus on your program's specific code.  In the above example, the rest of your application can call _saver.save data_ without regard for where the file ultimately ends up.

wanted-recipes.textile

@@ -133,7 +133,6 @@ h2. Design patterns
 
 * Structural Patterns
 ** Adapter
-** Bridge
 ** Composite
 ** Facade
 ** Flyweight