object-oriented lessons for a service-oriented world Railsberry 2013 Krakow, Poland 

Chris Kelly in meatspace 

amateurhuman on the interwebs 

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This is a conversation about ideas. It is not a prescription for how you have to do it. 

San Francisco Krakow Portland Crieff Hydro Warsaw Denver 

Lynx (web browser) - Wikipedia, the free encyclopedia (p1 of 26) #Edit this page Wikipedia (en) copyright Wikipedia Atom feed Lynx (web browser) From Wikipedia, the free encyclopedia Jump to: navigation, search Not to be confused with Links (web browser) or LynxOS. Original author(s) Lou Montulli, Michael Grobe, Charles Rezac Developer(s) Thomas Dickey Initial release 1992 (1992) Lynx is a highly configurable text-based web browser for use on cursor-addressable character cell terminals.^[1]^[2] It is the oldest web browser currently in general use and development,^[3] having started in 1992 and as of 2013^[update], 21 years later, still in use and development. Arrow keys: Up and Down to move. Right to follow a link; Left to go back. H)elp O)ptions P)rint G)o M)ain screen Q)uit /=search [delete]=history list 

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animated gifs 

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MONORAIL 

SOFTWARE SO WHAT YOU WANT IS ARCHITECTURE 

Software architecture? Did you just tell me to go F*@< myself? 

NETWORK-BASED APPLICATION SOFTWARE 

Monorail Cache Database 

Monorail Cache Database 

Monorail Cache Database 

Monorail Cache Database 

Special Snowflake YouR is a application 

Special Snowflake YouR is a application that breaksevery time you change anything 

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DEPENDENCIES 

OBJECT ORIENTED DESIGN D E P E NDE N C I E S 

State Behavior a thorough and complete analysis of objects* *100% accurate 0% of the time 

State Behavior a thorough and complete analysis of objects* *100% accurate 0% of the time 

State Behavior a thorough and complete analysis of objects* ^ MORE *100% accurate 0% of the time 

Cool story, bro. But we’re talking about applications talking over http. 

HELLO my name is HTTP Object Model 

HELLO my name is REST 

DRY SOLID LAW OF DEMETER seperation of concerns Single-responsibility principle Open-Closed Liskov Substitution Interface Segregation Dependency Inversion Don’t Repeat Yourself Encapsulation 

Single Responsibility Do one thing, and do it well. Do the smallest thing possible, and nothing more. Make things as simple as possible, but not simpler. Cohesive, everything it does should be related to its purpose. 

Repeat Yourself Every piece of knowledge within a system must have single, unambiguous, authoritative representation 

Depend on Behavior not on data 

Dependency Inversion Dependency Inversion 

DEMETER LAW OF More like guidelines of Demeter 

Dependency Injection 

Service Database Service Service Service Service Service 

Public Service Announcement Cache is King Network-based software applications mean more overhead. Serialization is expensive, do yourself a favor and don’t do it when you don’t have to. Cache-control and etag headers are a services best friend. Caching is a first order feature. 

MESSAGES 

class Orders < ApplicationController::Base def index @orders = Order.all respond_to do |format| format.html format.json { render json: @orders } end end end Not a Application Programming Interface 

Nouns VERBS In object-oriented design, classes are And our messages are often 

/getUsers /verifyEmailAddress /getOrders /updateShippingAddress 

GET PUT POST DELETE HTTP already has some verbs But they’re kind of crudy 

What about hypermedia? 

This is not your Rails’ REST https://api.example.org/accounts/23/orders/37 

REST HYPERMEDIA COMBINES A MEDIA TYPE & LINK RELATIONS 

{ “_links”: { “self”: { “href”: “/orders” }, “next”: { “href”: “/orders?page=2” }, “find”: { “href”: “/orders/{id}”, “templated”: true }, “_embedded”: { “orders”: [{ “_links”: { “self”: { “href”: “/orders/123” } }, “total”: 1337.00 Behavior { { State 

{ “_links”: { “self”: { “href”: “/orders” }, “next”: { “href”: “/orders?page=2” }, “find”: { “href”: “/orders/{id}”, “templated”: true }, “_embedded”: { “orders”: [{ “_links”: { “self”: { “href”: “/orders/123” }, “cancel”: { “href”: “/orders/123/cancel” } }, Behavior { { State 

Behavioral API by Example 

Get a single issue GET /repos/:owner/:repo/issues/:number { "url": "https://api.github.com/repos/octocat/Hello-World/issues/134 "html_url": "https://github.com/octocat/Hello-World/issues/1347", "number": 1347, "state": "open", "title": "Found a bug", "body": "I'm having a problem with this.", "user": { "login": "octocat", "id": 1, 

Close an issue PATCH /repos/:owner/:repo/issues/:number { "state": "closed" } 

Get a pull request GET /repos/:owner/:repo/pulls/:number { "url": "https://api.github.com/octocat/Hello-World/pulls/1", "html_url": "https://github.com/octocat/Hello-World/pulls/1", "diff_url": "https://github.com/octocat/Hello-World/pulls/1.diff", "patch_url": "https://github.com/octocat/Hello-World/pulls/1.patch "issue_url": "https://github.com/octocat/Hello-World/issue/1", "number": 1, "state": "open", "title": "new-feature", "body": "Please pull these awesome changes", 

Merge Button PUT /repos/:owner/:repo/pulls/:number/merge { # Optional Message "message": "YOLO" } TM 

The Good The Bad The Ugly Link relations are already appearing in media types You can implement custom media types The necessary HTTP verb is a missing 

Thanks for the chat. @amateurhuman