# IT:AD:Patterns #



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* [[../|(UP)]]
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* See also:
    * [[IT/AD/Principles/]]
    * [[IT/AD/Design/]]
    * [[Business/Concepts/Pattern/]]
* http://skysigal.com/blogs/sigal/sky/errata/entries/patterns_to_thrive._always


</callout>


<panel title="Summary">

<uml>
!includeurl http://skysigal.com/_media/resources/configuration/plantuml/minimalist.txt

class "Patterns" as P
class "Software Architecture Patterns" as SAP
class "Software Design Patterns" as SDP
class "Algorithm strategy patterns" as SDP1
class "Computational design patterns" as SDP2
class "Execution patterns" as SDP3
class "Implementation strategy patterns" as SDP4
class "Structural design patterns" as SDP5

P <|-- SDP
P <|-- SAP

SDP <|-- SDP1
SDP <|-- SDP2
SDP <|-- SDP3
SDP <|-- SDP4
SDP <|-- SDP5


class "Creational Patterns" as SDCRP
class "Structural Patterns" as SDSP
class "Behavioral Patterns" as SDBP
class "Concurrency Patterns" as SDCOP

SDP5 <|-- SDCRP
SDP5 <|-- SDSP
SDP5 <|-- SDBP
SDP5 <|-- SDCOP



</uml>


</panel>


## Essential Patterns ##

They're *all* important! But if one had to hone in on essential ones to understand before attempting resilient software, I'd propose starting with getting the following under your belt:

* [[IT/AD/Patterns/DDD/]]
    * [[IT/AD/Patterns/Dependency Injection Strategy/]]
* [[IT/AD/Patterns/SOLID/]]
* [[IT/AD/Patterns/Vendors Suck Strategy/]]
* [[IT/AD/Patterns/Convention over Configuration Strategy/]]
* [[IT/AD/Patterns/Repository Pattern/]]
* [[IT/AD/Patterns/Command Pattern/]]
* [[IT/AD/Patterns/CQRS/]]
* [[IT/AD/Patterns/TripleA's Strategy/]]



## Strategies ##

* [[IT/AD/Patterns/Vendors Suck Strategy/]]
* [[IT/AD/Patterns/MS is a Vendor Strategy/]]: you get the point...
* [[IT/AD/Patterns/MS Sells VS (not Good Practices) Strategy]]: When in doubt, a good thing to remember...
* [[IT/AD/Patterns/Namespace As Problem Boundary Strategy/]]: a lot of devs don't know what a Namespace is for.
* [[IT/AD/Patterns/Gift Package Strategy/]]: quick: what's the first thing the client experiences of your app? The [[IT/#UI/]]?
* [[IT/AD/Patterns/Complex is not Complicated Strategy/]]
* [[IT/AD/Patterns/AppSettings Are Dead Strategy/]]
* [[IT/AD/Patterns/Enums Start with Undefined Strategy/]]
* [[IT/AD/Patterns/Version Your Messages Strategy/]]
* [[IT/AD/Patterns/SASS/]]
* [[IT/AD/Patterns/Naming Strategies/]]
* [[IT/AD/Patterns/Convention over Configuration Strategy/]]



## Documentation ##
* [[IT/AD/Patterns/State Boldy, Justify, Give Alternatives Strategy/]]

## App Architecture  Patterns ##
* [[IT/AD/Patterns/DDD/]]: the most important pattern an application architect can learn.
* [[IT/AD/Patterns/DDD/Entities/]]
* [[IT/AD/Patterns/Tier Strategy/]]
* [[IT/AD/Patterns/SASS/]]


## Architecture Strategies ##
* Usability:
    * [[IT/AD/Patterns/Help is for Failures Strategy/]]: if your UI needs a help doc to explain it...it's poor [[IT/#UX/]] design. 
* Security:
    * [[IT/AD/Patterns/TripleA's Strategy/]]: Authentication, Authorisation, Auditing (if your not Auditing, you're security isn't up to snuff yet).
    * [[IT/AD/Patterns/Security is an Application Concern/]]
    * [[IT/AD/Patterns/Don't drop your pants Strategy/]]: don't round-trip your datastore Ids to the client.
	* [[IT/AD/Patterns/Secure the Line Strategy/]]: ensure SSL is enabled.
* API:
    * [[IT/AD/Patterns/Version Your Messages Strategy/]]
    * [[IT/AD/Patterns/Enums Start with Undefined Strategy/]]
* Testability:
    * [[IT/AD/Patterns/AppHost Strategy/]]
* Modularity:
    * [[IT/AD/Patterns/Composite Application Strategy/]]
    * [[IT/AD/Patterns/Contract First Development Strategy/]]
* Maintainability:
    * [[IT/AD/Patterns/Vendors Suck Strategy/]]
    * [[IT/AD/Patterns/MS is a Vendor Strategy/]]: you get the point...
    * [[IT/AD/Patterns/Everything is Perishable Strategy/]]: any tech is like fruit...tempting...but perishable. Protect your BIP by keeping it at arms 
    * [[IT/AD/Patterns/Egg Yolk Strategy/]]: encapsulate dependencies. The Drug-Mule Strategy.
    * [[IT/AD/Patterns/Many Assemblies Strategy/]]
    * [[IT/AD/Patterns/Extension Methods Strategy/]]:also known as the Cross-Dresser Strategy.
* Responsiveness:
    * [[IT/AD/Patterns/Chunky over Chatty Strategy/]]: and no -- it's not the same as *"Rottweillers are better than Chiwawas Strategy"*.
    * [[IT/AD/Patterns/Cache Like Crazy Strategy/]] (or [[IT/AD/Patterns/Cache Is King Strategy/]])
    * [[IT/AD/Patterns/Dual Access To Data/]]


http://tvnz.co.nz/national-news/govt-cannot-guarantee-public-information-protected-english-5399955


## App Component  Patterns ##
* [[IT/AD/Patterns/Head Last Pattern/]]: hold off on the UX or your app will bind itself too quickly to the UX framework.
* [[IT/AD/Patterns/Lowest Framework Profile/]]
* [[IT/AD/Patterns/Minimal Dependency Cardinality/]]
* [[IT/AD/Patterns/Dependency Wrapping Strategy/]]
* [[IT/AD/Patterns/Factories/]]
* [[IT/AD/Patterns/Service Pattern/]]
* [[IT/AD/Patterns/Objects as Messages Strategy/]]
* [[IT/AD/Patterns/CQRS/]]: Command Query Responsibility Segregation (separation of data retrieval from data modification).
* [[IT/AD/Patterns/Specification Pattern/]]
* [[IT/AD/Patterns/IoC/]]
* [[IT/AD/Patterns/DRY Strategy/]]
* [[IT/AD/Patterns/DTO Strategy/]]






## Development Patterns ##

* [[IT/AD/Patterns/SOLID/]]: the most useful pattern that a developer can learn.
* [[IT/AD/Patterns/Dependency Injection Strategy/]]
* [[IT/AD/Patterns/CQRS/]]
* [[IT/AD/Patterns/Command Pattern/]]
* [[IT/AD/Patterns/ACID/]]
* [[IT/AD/Patterns/Repository Pattern/]]
* [[IT/AD/Patterns/UnitOfWork Pattern/]]
* [[IT/AD/Patterns/IdentityMap/]]
* [[IT/AD/Patterns/KISS Strategy/]]
* [[IT/AD/Patterns/SOC/]]: Separation of Concerns Strategy

## Persistence Patterns ##

* [[IT/AD/Patterns/Reference Data Strategy/]]
* [[IT/AD/Patterns/Domain First Strategy/]]
* [[IT/AD/Patterns/Enums Mapped To Code Tables Strategy/]]
* [[IT/AD/Patterns/Localisable Data Strategy/]]



## Presentation Patterns ##

* [[IT/AD/Patterns/WIMP/]]
* [[IT/AD/Patterns/MVC/]]
* [[IT/AD/Patterns/MVP/]]



## UX Patterns 

* [[IT/AD/Patterns/Views are not Screens Strategy/]]
* [[IT/AD/Patterns/Page Number isn't a Search Criteria Strategy/]]
* [[IT/AD/Patterns/Single Page Website Strategy/]]
* [[IT/AD/Patterns/Less is More Strategy/]]
* [[IT/AD/Patterns/It's all Hierarchical after all/]]
* [[IT/AD/Patterns/Avoid combining I/O Views/]]: search forms and result lists should be kept separate. 



## GoF Patterns


### Creational Patterns 

* **[[IT/AD/Patterns/Abstract Factory/]]:**  Creates an instance of several families of classes. Provide an interface for creating families of related or dependent objects without specifying their concrete classes.
* **[[IT/AD/Patterns/Builder/]]:** Separates object construction from its representation. Separate the construction of a complex object from its representation so that the same construction processes can create different representations.
* **[[IT/AD/Patterns/Factory Method/]]:** Creates an instance of several derived classes. Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.
* **[[IT/AD/Patterns/Prototype/]]:** A fully initialized instance to be copied or cloned. Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.
* **[[IT/AD/Patterns/Singleton/]]:** A class of which only a single instance can exist. Ensure a class only has one instance, and provide a global point of access to it.


### Structural Patterns ###

* **[[IT/AD/Patterns/Adapter/]]:** Match interfaces of different classes.Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn’t otherwise because of incompatible interfaces.
* **[[IT/AD/Patterns/Bridge/]]:** Separates an object’s interface from its implementation. Decouple an abstraction from its implementation so that the two can vary independently.
* **[[IT/AD/Patterns/Composite/]]:** A tree structure of simple and composite objects. Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly.
* **[[IT/AD/Patterns/Decorator/]]:** Add responsibilities to objects dynamically.  Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality.
* **[[IT/AD/Patterns/Facade/]]:** A single class that represents an entire subsystem. Provide a unified interface to a set of interfaces in a system. Facade defines a higher-level interface that makes the subsystem easier to use.
* **[[IT/AD/Patterns/Flyweight/]]:** A fine-grained instance used for efficient sharing. Use sharing to support large numbers of fine-grained objects efficiently. A flyweight is a shared object that can be used in multiple contexts simultaneously. The flyweight acts as an independent object in each context — it’s indistinguishable from an instance of the object that’s not shared.
* **[[IT/AD/Patterns/Proxy/]]:** An object representing another object. Provide a surrogate or placeholder for another object to control access to it.


### Behavioral Patterns
* **[[IT/AD/Patterns/Chain of Responsibility/]]:**  A way of passing a request between a chain of objects. Avoid coupling the sender of a request to its receiver by giving more than one object a  chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.
* **[[IT/AD/Patterns/Command Pattern/]]:** Encapsulate a command request as an object. Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.
* **[[IT/AD/Patterns/Interpreter/]]:** A way to include language elements in a program. Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.
* **[[IT/AD/Patterns/Iterator/]]:** Sequentially access the elements of a collection. Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
* **[[IT/AD/Patterns/Mediator/]]:** Defines simplified communication between classes. Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.
* **[[IT/AD/Patterns/Memento/]]:** Capture and restore an object's internal state. Without violating encapsulation, capture and externalize an object’s internal state so that the object can be restored to this state later.
* **[[IT/AD/Patterns/Observer/]]:** A way of notifying change to a number of classes. Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.
* **[[IT/AD/Patterns/State/]]:** Alter an object's behavior when its state changes. Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.
* **[[IT/AD/Patterns/Strategy/]]:** Encapsulates an algorithm inside a class. Define a family of algorithms, encapsulate each one, and make them interchangeable.            Strategy lets the algorithm vary independently from clients that use it.
*  **[[IT/AD/Patterns/Template/]]:** Defer the exact steps of an algorithm to a subclass. Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.
* **[[IT/AD/Patterns/Visitor/]]:** Defines a new operation to a class without change. Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.
I must also mention and credit goes to http://www.dofactory.com/Patterns/Patterns.aspx for the most of the above information.



## Communication Patterns ##

* http://en.wikipedia.org/wiki/Robustness_principle


## Gaming Patterns

* http://gameprogrammingpatterns.com/


##Warnings ##

* [[IT/AD/Patterns/Designing from the UI will kill your company/]]


## Resources ##

* [Silk](http://msdn.microsoft.com/en-us/library/hh396380.aspx)
* [http://prodinner.codeplex.com/](http://prodinner.codeplex.com/)
* [http://www.asp.net/mvc/samples](http://www.asp.net/mvc/samples)
* https://en.wikipedia.org/wiki/A_Pattern_Language