Advanced OOP Laws Principles Idioms Clint Edmonson

what is oop?

abstraction encapsulation inheritance polymorphism

structural

domain driven design All software can be composed of only four elements: - Value objects - Entities - Services - Modules

All software can be composed of only four elements:

- Value objects

- Entities

- Services

- Modules

separation of concerns Every class and method should have a single responsibility . All its functionality should be narrowly aligned with that responsibility.

Every class and method should have a single responsibility .

All its functionality should be narrowly aligned with that responsibility.

the DRY principle Don’t repeat yourself . Don’t repeat yourself. Don’t repeat yourself.

Don’t repeat yourself .

Don’t repeat yourself.

Don’t repeat yourself.

theory of one right place There should be only one right place for a piece of nontrivial of code, and one right place to make a likely maintenance change.

There should be only one right place for a piece of nontrivial of code,

and one right place to make a likely maintenance change.

unit of work Define entity families around transactional boundaries.

Define entity families around transactional boundaries.

the open-closed principle Software entities (classes, methods, and modules) should be open for extension but closed for modification .

Software entities (classes, methods, and modules) should be

open for extension

but closed for modification .

design by contract Fortify your methods through preconditions , post-conditions , and invariant assertions.

Fortify your methods through

preconditions ,

post-conditions ,

and invariant assertions.

creational

declarative programming Use attributes to describe what you want to happen and leverage a framework will take care of the how .

Use attributes to describe what you want to happen and leverage a framework will take care of the how .

the provider model Define a public service façade that uses an private implementation to perform all of it’s work.

Define a public service façade that uses an private implementation to perform all of it’s work.

inversion of control Leverage configuration files to automatically create objects as they are needed.

Leverage configuration files to automatically create objects as they are needed.

dependency injection Declaratively describe dependencies between classes and an IOC framework can automatically instantiate all of them.

Declaratively describe dependencies between classes and an IOC framework can automatically instantiate all of them.

object : relational mapping Leverage IOC and dependency injection to automatically load entities from your database.

Leverage IOC and dependency injection to automatically load entities from your database.

behavioral

principle of scenario driven design All functionality should be driven by usage scenarios.

All functionality should be driven by usage scenarios.

occam ’ s razor The simplest solution is usually the best .

The simplest solution is usually the best .

the pareto principle For many phenomena, 80% of the consequences stem from 20% of the causes

For many phenomena, 80% of the consequences stem from 20% of the causes

the law of demeter “ Don’t talk to your neighbor’s neighbor!” An object should only call methods and properties belonging to: - Itself - Any parameters passed in - Objects it creates - Child components

“ Don’t talk to your neighbor’s neighbor!”

An object should only call methods and properties belonging to:

- Itself

- Any parameters passed in

- Objects it creates

- Child components

principle of least resource usage The minimal amount of computational resources should be used to solve a particular need.

The minimal amount of computational resources should be used to solve a particular need.

principle of least privilege Provide the minimal level of access necessary for consumers to do their job. Combined with the previous principle… Classes and methods should be as static and private as possible.

Provide the minimal level of access necessary for consumers to do their job.

Combined with the previous principle…

Classes and methods should be as static and private as possible.

the liskov substitution principle A derived class should be completely and transparently substitutable for it’s base class.

A derived class should be completely and transparently substitutable for it’s base class.

idempotents Transactional systems should allow the same information to be received multiple times without being reprocessed .

Transactional systems should allow the

same information to be received multiple times without being reprocessed .

cyclomatic complexity The depth of nested logic should be kept to a minimum .

The depth of nested logic should be kept to a minimum .

What are your principles?

Questions & Discussion

Books Code Complete - McConnell Effective C# - Wagner Framework Design Guidelines – Cwalina & Abrams Writing Solid Code - Maguire Links Application Architecture for .NET OO Design Principles Principles of Object Oriented Design Separation of Concerns (Wikipedia) References

Books

Code Complete - McConnell

Effective C# - Wagner

Framework Design Guidelines – Cwalina & Abrams

Writing Solid Code - Maguire

Links

Application Architecture for .NET

OO Design Principles

Principles of Object Oriented Design

Separation of Concerns (Wikipedia)

Clint Edmonson [email_address] http://www.notsotrivial.net

[email_address]

http://www.notsotrivial.net

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