SOLID & concrete

class: center, middle
# SOLID & concrete

.b[[@abelar_s](https://twitter.com/abelar_s) -
[@ParisRB](https://twitter.com/parisrb) -
[@RailsGirlsParis](https://twitter.com/railsgirlsparis)]
 
[maitre-du-monde.fr](maitre-du-monde.fr)

.contrib[[Contribute to this talk on GitHub!](https://github.com/abelards/abelards.github.com/edit/master/talks/SOLID.html)]

???

---
class: center, middle
# SOLID & concrete
## SRP + OCP + LSP + ISP + DIP

.b[[@abelar_s](https://twitter.com/abelar_s) -
[@ParisRB](https://twitter.com/parisrb) -
[@RailsGirlsParis](https://twitter.com/railsgirlsparis)]
 
[maitre-du-monde.fr](maitre-du-monde.fr)

.contrib[[Contribute to this talk on GitHub!](https://github.com/abelards/abelards.github.com/edit/master/talks/SOLID.html)]

???

---
class: center, java
# SRP 4 JAVA
## Single Responsibility Principle

"A class should only have a single responsibility"

---
class: center, rationale
# SRP Rationale
## Single Responsibility Principle

"A responsibility is a reason to change"

---
class: center, ruby
# SRP 4 RUBY
## Single Responsibility Principle

- `check_state`, `to_state_x` # also sends mail

- right_state?
- send_email
- trigger: send_email_when_right_state

???
Triggers: when I create an order in the right state, send an email.

---
class: center, koans
# SRP Koäns
## Single Responsibility Principle

- [175 Flat Shark](http://thecodelesscode.com/case/175)
 - [83 Consequences](http://thecodelesscode.com/case/83)
 - [117 Bareback](http://thecodelesscode.com/case/117)
 - [167 Back to Basics](http://thecodelesscode.com/case/167)

---
class: java
# OCP 4 JAVA
## Open-Closed Principle

"Software entities … should be open for extension, but closed for modification."

Abstract classes all the way down.

---
class: rationale
# OCP Rationale
## Open-Closed Principle

Isolation, tests, change.

Libraries' reuse, adding meaning to basic structures...

---
class: ruby
# OCP 4 RUBY
## Open-Closed Principle

OMG we're Rubyists! o_O;

JK we just limit on monkeypatching, metaprog, and...
it's message passing time! <3

---
class: center, koans
# OCP Koäns
## Open-Closed Principle

- [22 Safety](http://thecodelesscode.com/case/22)
 - [110 The Trunk](http://thecodelesscode.com/case/110)
 - [112 Speak to me](http://thecodelesscode.com/case/112)
 - [177 The Tool-Shed](http://thecodelesscode.com/case/177)

---
class: center, java
# LSP 4 JAVA
## Liskov Substitution Principle
### Javaists

"Let Φ(x) be a property provable about objects x of type T.
 Then Φ(y) should be true for objects y of type S
 where S is a subtype of T."

A Rectangle is a Square, not the other way around.

---
class: center, rationale
# LSP Rationale
## Liskov Substitution Principle
### Rationale

- don't mess up with the pointers

"Be laxist in what you accept, strict in what you give."

- keep the same interface
- accept more data
- grow

---
class: center, ruby
# LSP 4 RUBY
## Liskov Substitution Principle
### Rubyists

- Composition over inheritance
- Methods and fields look the same
- Duck-typing makes many patterns easier
- Introspection makes LAZINESS easier!

---
class: center,koans
# LSP Koäns
## Liskov Substitution Principle
### Koäns

- [83 Consequences](http://thecodelesscode.com/case/83)
 - []()
 - []()
 - []()

---
# ISP 4 JAVA
## Interface Separation Principle

"many client-specific interfaces are better than one general-purpose interface."

---
# ISP Rationale
## Interface Separation Principle

- "Duplication is far cheaper than the wrong abstraction"
- Reasons for change

---
# ISP 4 RUBY
## Interface Separation Principle

- Clever code is too clever

---
# ISP Koäns
## Interface Separation Principle

- [213 The Imperfect Mirror](http://thecodelesscode.com/case/213?)
 - [230 All Together Now](http://thecodelesscode.com/case/230)

---
# DIP 4 JAVA
## Dependency Inversion Principle

"one should Depend upon Abstractions. Do not depend upon concretions."

---
# DIP Rationale
## Dependency Inversion Principle

You can trust the idea to persist.
You cannot trust the implementation.

You can trust your friends, not their address.
Leaky abstractions.

---
# DIP 4 RUBY
## Dependency Inversion Principle

I give you the info I have, you don't have to ask me.

---
# DIP Koäns
## Dependency Inversion Principle

---
class: left
# SOLID!

* `S`ingle Responsibility
* `O`pen-Closed
* `L`iskov Substitution
* `I`nterface Separation
* `D`ependency Injection

---
class: left
# SOLID?

* don't make a mess
  * don't mix weird things
  * don't let people mess internally
* who should be responsible
  * if it's your job, do it
  * if not your job, ask others
* keep things in a single brain
  * similar things should look similar
  * different things should look different

---
class: left
# ARCHI

* `A`nticipate
* `R`easons for
* `C`hange, be
* `H`ostile to
* `I`ntricacies

---
class: center, middle, happy
# Questions?

.b[[@abelar_s](https://twitter.com/abelar_s) -
[@ParisRB](https://twitter.com/parisrb) -
[@RailsGirlsParis](https://twitter.com/railsgirlsparis)]
 
[maitre-du-monde.fr](maitre-du-monde.fr)

.contrib[[Contribute to this talk on GitHub!](https://github.com/abelards/abelards.github.com/edit/master/talks/SOLID.html)]

---
class: center, middle, happy
# Thanks!

.b[[@abelar_s](https://twitter.com/abelar_s) -
[@ParisRB](https://twitter.com/parisrb) -
[@RailsGirlsParis](https://twitter.com/railsgirlsparis)]
 
[maitre-du-monde.fr](maitre-du-monde.fr)

.contrib[[Contribute to this talk on GitHub!](https://github.com/abelards/abelards.github.com/edit/master/talks/SOLID.html)]