1.
Demand-driven architecture

2.
Problems of the current
architecture

3.
= REST?

4.
Let’s do some REST!

5.
Let’s build an app
- post things
- comment on things
- … profit?
Posts
Users
Comments

6.
Let’s build an app

7.
Let’s build an app

8.
Problems?
- unnecessary complex ajax orchestration
- edge cases
- many points of failure
- a lot of data to download
- one part always waits for the other

9.
Let’s build an app

10.
Let’s build an app

11.
Problems?
- duplication of data
- maintenance
- cascading changes through the entire app
- one part always waits for the other

12.
The solution
- Stop endpoint overload
- Shift ownership over data to client
- Server returns exactly what the client needs
- Exactly what netflix and facebook independently did!

13.
om

14.
Disclaimer
- Examples are in clojure

15.
“Client describes data it needs”
(defui Post
Object
(render [this]
(view nil
(text nil (get (om/props this) :username))
(text nil (get (om/props this) :content)))))

16.
“Client describes data it needs”
(defui Post
static om/IQuery
(query [this]
'[{:user [:username]} :content])
Object
(render [this]
(view nil
(text nil (get (get (om/props this) :user) :username))
(text nil (get (om/props this) :content)))))

17.
“Client describes data it needs”
(defui Post
static om/Ident
(ident [this {:keys [id]}]
[:post/by-id id])
static om/IQuery
(query [this]
'[{:user [:username]} :content :id])
Object
(render [this]
(view nil
(text nil (get (get (om/props this) :user) :username))
(text nil (get (om/props this) :content)))))

18.
“Client describes data it needs”
(defui TimelineComponent
static om/IQuery
(query [this]
(let [subquery (om/get-query Post)]
`[{:app/posts ~subquery}]))
Object
(render [this]
(let [{:keys [app/posts]} (om/props this)]
(view nil
(apply view nil
(map post posts))))))

19.
DEMO

20.
Advantages?
- server API doesn’t need updates
- downloaded data is as small as possible
- no ajax coordination
- focus is on client and components
- component re-usability
- usable today

21.
Talks
- “om next” by David Nolen
- “Why Falcor?” by Jafar Husain
- “Relay: An application framework for React” by Josep Savona

22.
Questions?