Created Introduction to Drops (markdown)

Introduction-to-Drops.md

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+# Liquid Drops
+
+Drops let you provide the user with custom functionality. They're very much like a standard Ruby class, but have all un-needed and potentialy dangerous methods removed. From the user's perspective a drop acts very much like a Hash, thought methods are accessed with dot-notation aswell as element selection. A drop method cannot be invoked with arguments. Drops are called just-in-time thus allowing you to lazily load objects.
+
+## Standard drop methods:
+
+before_method(method):
+
+Called once for every invokation, even if the destination method doesn't exist. Can be used to provide dynamically named methods.
+
+Example:
+
+    class MembersDrop < Liquid::Drop
+
+      def before_method(method)
+        user = User.find_by_name(method)
+        user ? UserDrop.new(user) : nil
+      end
+
+    end
+
+### View
+
+    {% assign user = members.ian %} {{ user.name }}
+
+invoke_drop(method):
+
+Called by liquid to invoke the target drop method.
+
+has_key(name):
+
+Currently returns true regardless.
+
+to_liquid:
+
+Returns the drop instance.
+
+### Drop usage:
+
+    class ProductDrop < Liquid::Drop
+
+      def initialize(product)
+        @product = product
+      end
+
+      def name
+        @product[:name]
+      end
+
+      def description
+        @product[:description]
+      end
+
+      def price
+        @product[:price]
+      end
+
+    end
+
+### Controller 
+
+    template = Liquid::Template.parse( File.read( product_view.liquid ) ) template.render( { :product => ProductDrop.new(@product) } )
+
+### View
+
+    Viewing product: {{ product.name }} <br/><br /> {{ product.description }} <br /> £{{ product.price }}