Design Patterns Part 1 – You Create Me!

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This week we’re tackling the first section of seminal Design Patterns book: Creational Patterns.

We discuss factories of factories, “bullet hell” games, pathological liars, and Allen’s lack of voice.

Big thanks to @rajsotweet for calling us out and getting us motivated to record!

Points of Interest

• .NET Framework 4.5.2 is out!
• ASP vNext
• Awesome stats from Kaspersky!
• Entity Framework 7
• PowerShell Module Design Rules (and When to Bend Them)
• NuGet package that integrates PowerShell into MSBuild as a first-class citizen
• Strongly Named Assemblies in Nuget

Fun Stuff!

• Rogue Code
• Influx
• Watch_Dogs

 

Why study design patterns?

• Famous “Gang of Four” book published in 1994, still in first edition!
• “They help make a system independent of how its objects are created, composed, and represented”
• Promote composition over inheritance (smaller, more focused classes that can be recomposed into different functionality – Do one thing well philosophy)

Patterns divided Into 3 Parts

• Creational Patterns
• Structural Patterns
• Behavioral Patterns

Main Creational Patterns

• Factory Methods
• Factories
• Builders
• Prototypes
• Singletons

Factories and Factory Methods Patterns

• “Nobody really buys hammers anymore.”
• Centralize object creation
• Decouples class creation from logic
• When do you know that you need a factory?
• Real world example: AWS SDK
• Reflection of Control

Builder Pattern

• Great way to build complex objects
• Real world examples: StringBuilder, UriBuilder

Prototype Pattern

• Cloning at runtime!
• Prototype Example

 

• Real world examples: ICloneable and JavaScript

Singleton Pattern

• One object to coordinate actions across the system
• Globally scoped, often to avoid dependency passing/injecting
• Mandate their own creation/lifecycle/persistance
• Single instance of a class (restricts the instantiation of a class to one object)
• Different implementations: Static Classes, Inner Objects / Double Check Locking, Lazy
• Any chance your constructor will fail? Don’t use static constructors!
• Singletons are Pathological Liars
• Outlaw vs Skeet, static vs double checked locking singletons

Additional Resources

• Gang of Four Book
• Exploring the Factory Design Pattern
• C# in Depth, 3rd Edition by Jon Skeet
• Design Patterns in the .Net Framework
• Design Patterns Library

Tips / Tricks

• Bookmarks in Visual Studio
• Debugging Object Initializers (again, oops!)
• Click a word in your Visual Studio editor window, once the word highlights, use Ctrl + F3 to find the next instance of the word in the file
• Clean Code recommended using static methods instead of constructor overloads: static methods instead of constructor overloads Color.FromHex(“#ffff00”) instead of Color(“#ffff00”)

Thanks for listening!