Added the Template Method Pattern.

Author: randusr836

authors.md

@@ -21,6 +21,7 @@ The following people are totally rad and awesome because they have contributed r
 * Frederic Hemberger
 * Mike Hatfield *[email protected]*
 * [Anton Rissanen](http://github.com/antris) *[email protected]*
+* Calum Robertson *http://github.com/randusr836*
 * ...You! What are you waiting for? Check out the [contributing](/contributing) section and get cracking!
 
 # Developers

chapters/design_patterns/template_method.md

@@ -0,0 +1,45 @@
+---
+layout: recipe
+title: Template Method Pattern
+chapter: Design Patterns
+---
+## Problem
+
+You need to execute a series of steps according to some algorithm or recipe and wish to provide the implementation for any of the steps.
+
+## Solution
+
+Use the Template Method to describe each step in a superclass, delegating the implementation of each step to a subclass.
+
+For example, imagine you wish to model various types of document and each one may contain a header and a body.
+
+{% highlight coffeescript %}
+class Document
+	produceDocument: ->
+		@produceHeader()
+		@produceBody()
+
+	produceHeader: ->
+	produceBody: ->
+
+class DocWithHeader extends Document
+	produceHeader: ->
+		console.log "Producing header for DocWithHeader"
+
+	produceBody: ->
+		console.log "Producing body for DocWithHeader"
+
+class DocWithoutHeader extends Document
+	produceBody: ->
+		console.log "Producing body for DocWithoutHeader"
+
+doc1 = new DocWithHeader
+doc1.produceDocument()
+
+doc2 = new DocWithoutHeader
+doc2.produceDocument()
+{% endhighlight %}
+
+## Discussion
+
+In this example, there are two steps, one for producing a document header and the second for producing the document body; these two steps are given empty implementations in the superclass. The DocWithHeader implements both the body and header steps, whereas the DocWithoutHeader only impements the body step.