Aki Salmi: Object Oriented Views at I T.A.K.E. Unconference 2015

Object Oriented Views

Aki Salmi@rinkkasatiainen

Wednesday, May 20, 15

Programmer@Ambientia

skype: @rinkkasatiainentwitter: @rinkkasatiainenemail: [email protected]



Content

• Background• A way to solve• Discussion• Open Space: Mob Programming?


Very Brief Background

• Confluence plugin


We have all seen


Controllers like


This


/INDEX (1 of many actions)

ParamsService

“DAO”“or not DAO”

DAO-DAO-DAO

ServiceService

DomainServiceRender


Not that, not today


Let’s assume we’re working with thin

controllers


Have we seen


views like


thisOnly today: logic in a view


So how then?


How about Code I’ve written myself?


Not much better


A Deeper Dive

Params

BUILDCONTEXT

GET MODEL

RENDEROR RENDER


But there is a catch


Render Many BlogsOr 1, or 0


... based on object types


Build a ‘different’ domain entity?

Build ‘real’

Domain

Build ‘real’

Domain


Build a ‘different’ Context

BUILD context

Diff context

no context


Render ‘different’ template

Templ_0Templ_1

Templ_n


Seems like a violation of SRP

(Single Responsibility Principle)


What did we see

• build parameters• build context (on 2 places)• build domain• render different data, differently, based

on the domain entity


Visually

Controller

HTTP GET

Domain

View 0 View 1 View N


It works


..sort of

• most of the bugs I introduced, were on this behavior of the system.• This class• Concepts introduced by this class• Integration with Confluence API

• especially ‘null’s


What IF

Controller

HTTP GET

Domain

View 0 View 1 View N


What IF...C’s responsibility

• Given a set of parameters...• Build Model (service / repository) • Render Template with model given

• and let other’s to figure out which template to render


Decorate / Exhibit

Controller

HTTP GET

Domain

View

Exhibit

1) build model

2) render

3) exhibit

View tmpl

4) render


How does it work


few design decision done by me

• avoid nulls • separate Read Model from Write Model• 1st class collections• Separated Query and Command

Controller (sort of CQRS)


Domain Entity: Group

<if> ReadOrWriteModel

<if> ReadModel <if> WriteModel

GroupEntity GroupDescrGroupList








GroupEntity* immutable

* final private prop* behavior rich

GroupDescriptor* public properties

* tiny behavior

AGroupThatDoesNotExistYet

AGroup








GroupList* behavior: iterate


Introducing Exhibits

• Introduced by Avdi Grimm• sort of presenter-decorator


Exhibit Characteristics

• Wraps a single model instance• Is a true Decorator• Brings together model and context• Encapsulates the decision about how to

render an object• May modify the behavior of an object


Exhibit BExhibit A

Exhibit visually

Model object


Exhibits: Group

<if> Exhibit+ renderBody()

GroupListExh GroupList

GroupExhibit GroupEntity

EditGroupExh GroupDesc

GroupWPicture


Exhibits: Group

GroupListExh ListView

GroupExhibit ShowGroup

EditGroupExh GroupDesc

GroupWPicture ShowGPicture


REST viewHTTP PATH Contr#Action Domain Class

GET /foo(.:format) foos#index FooList

POST /foo(.:format) foos#create FooDescriptor

GET /foo/new foos#new FooDescriptor

GET /foo/:id/edit foos#edit FooDescriptor

GET /foo/:id foos#show FooEntry

PATCH/PUT /foo/:id foos#update FooDescriptor

DELETE /foo/:id foos#delete FooDescriptor


Creating exhibits

public exhibit(ReadWriteModel model){for_each( exhibit: exhibit_classes ){

if( exhibit.applicableTo( model )// wrap model to exhibit and serve exhibit as new model

}}


Creating exhibitsthe ruby way 1/2

Avdi Grimm: Object on Rails, Listing 77


Creating exhibitsthe ruby way 2/2

Avdi Grimm: Object on Rails, Listing 77


Creating exhibitsthe Java 8 way 1/N


Time for some codeConfluence pluginVelocity templates


View


Controller


Exhibit A


Exhibit B


Exhibit C


Exhibit D


And visually


Surroundings

Exhibit templates


RemotePictureExhibit ||DefaultPictureExhibit

UserProfileExhibitCould be composite


Did it work - in retrospect

• No issues in production with this code• It is not, by far, easy to grasp. Without

someone explaining


What I did not show

• transformations of domain entities:• Request -> Write -> Persistence• Persistence -> Write (-> Read)

• Composite Exhibit - how to show 0, 1 or many concepts, dynamically, based on the ModelObject rendered


What could I experiment

• Capabilities for exhibits• Capability.mobile• Capability.REST• Capability.json


Thanks!Questions?

skype: @rinkkasatiainentwitter: @rinkkasatiainenemail: [email protected]


Aki Salmi: Object Oriented Views at I T.A.K.E. Unconference 2015

Technology