Merge pull request #78 from braydie/section-design-patterns

Create 09-Design Patterns.md

2-Intermediate/Judgment/09-Design Patterns.md

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+# Design Patterns
+
+Design Patterns can be seen as repeatable solutions to common problems arising in software design. They provide a great, language-agnostic
+way of talking about software architecture.
+
+"Head First Design Patterns" explains simply:
+
+> Design patterns don't go directly into your code, they first go into your BRAIN. Once you've loaded your brain with good working 
+knowledge of patterns you can start to apply them to your new designs
+
+There are a number of benefits to considering using a design pattern:
+
+- Helps your system prepare for accommodating change - an inevitability of software development
+- Allows for a shared language when describing a system - you can "say more with less"
+- Can lead to a better designed system (through *appropriate use* of a design pattern)
+
+There are 23 'Gang of Four' patterns that are generally considered the foundation for all other patterns. They are categorised into three groups: Creational, Structural and Behavioural. 
+
+## Criticisms
+
+[SourceMaking](https://sourcemaking.com/design_patterns) highlights some of the criticisms of using design patterns:
+
+ - Targets the wrong problem
+ - Lacks formal foundations
+ - Leads to inefficient solutions
+ - Does not differ significantly from other abstractions
+
+
+Some argue that design patterns ultimately boil down to good software design with careful consideration of SOLID principles.
+ [Jeff Atwood also has some thoughts on design patterns](http://blog.codinghorror.com/rethinking-design-patterns/)