MVS: An angular MVC

THINGS WRONG THAT I DID TO FIT THINGS IN SLIDES
DISCLAIMER
• Directives should use controller and bindToController
• Directives should never load resources, this should be done by
routes or under demand
• Use .factory to simplify and homogenize code 
(not .service neither .value)
• In a previous talk I said that model was plain JS data, sorry  
(plain data is the form, but does not defines a model)
• Use better variable names

MVC - MODEL THE
GREAT FORGOTTEN
FRONT MVC

TYPICAL ANGULAR CODE
AS SEEN ON SOME DOCS
(AND FROM SOME BEGINNERS)

<APP-BOOKS-LIST>
app.component(‘appBooksList’, {
template: ‘…’,
controller($http) {
$http.get(‘/api/v1/books’).then(response => {
this.books = response.data;
});
},
});

<APP-SCI-FI-BOOKS-LIST>
app.component(‘appSciFiBooksList’, {
controller($http) {
$http.get(‘/api/v1/books’).then(response => {
this.books = response.data.filter(isSciFi);
});
},
});

REFACTORING - SERVICE
THERE IS REPLICATED CODE
¡LET’S DO A SERVICE!

booksService
app.service(‘booksService’, ($http) => {
this.getList = () => {
return $http.get(‘/api/v1/books’).then(function(response) {
return response.data;
});
};
});
Acquires the responsibility for:
• R1: Know the API context Url
• R2: Create a remote connection
• R3: Transform response into usable object

<APP-BOOKS-LIST> & <APP-SCI-FI-BOOKS-LIST>
app.component(‘appBooksList’, {
controller(booksService) {
booksService.getList().then(books => {
this.books = books;
});
},
});
controller(booksService) {
this.books = books.filter(isSciFi);
});
},
});

PERFORMANCE - CACHING
OPS! WE ARE LOADING DATA TWICE
¡LET’S DO A CACHE!

booksService
Notice that:
• Repairs all directives at once
• Acquires one new responsibility (R4: manage cache)
return $http.get(‘/api/v1/books’, {cache:true}).then(response => {
});
};
});

booksService
Notice that:
• Repairs all directives at once
• Acquires one new responsibility (R4: manage cache)
if (!this.list) {
this.list = $http.get(‘/api/v1/books’).then(response => {
});
}
return this.list;
};
});
Alternate

NEW FEATURE - ONE BOOK
WE HAVE A VIEW THAT ONLY SHOWS ONE BOOK

<APP-BOOK-VIEW BOOK-ID=“ID”>
app.component(‘appBookView’, {
bindings: { bookId: ‘<‘ },
controller: function(booksService) {
booksService.get(this.bookId).then(book => { this.book = book; });
},
});

booksService (step1)
Notice that:
• What about repeating loading of books (R4: manage cache)
this.loadAll = function() {
});
};
this.load = (id) => {
return $http.get(‘/api/v1/books/’+id).then(response => {
});
};
});

• Uhmmmm… about R4… managing caches
this.loadAll = function() {
});
};
return $http.get(‘/api/v1/books/’+id, {cache:true}).then(response => {
});
};
});

WE ARE LOADING TWICE THE SAME BOOK!
It happens when:
• Loading one book
• Loading all books

OK… MAY BE IT’S OK LOAD TWICE
BUT NOT MORE TIMES
THE SAME BOOK
“We keep it simple…”

NEW FEATURE - UPDATE BOOK
WE HAVE A VIEW THAT MAKES AN UPDATE OF A BOOK
AND SHOWS THE CHANGES INTRODUCED BY API

<APP-BOOK-UPDATE BOOK-ID=“ID”>
app.component(‘appBookUpdate’, {
bindings: { bookId: ‘<‘, }
constructor(booksService) {
booksService.load(this).then(book => {
this.book = book;
});
this.update = () => {
booksService.update(this.book).then(updatedBook => {
this.book = updatedBook;
});
};
};
});

• Uhmmmm… about R4… managing caches
});
};
this.get = (id) => {
return $http.get(‘/api/v1/books/’+id, {cache:true})
.then(response => { return response.data; });
};
this.update = (book) => {
return $http.put(‘/api/v1/books/’+book.id)
.then(function(response) { return response.data; });
};
});

SHIT!

SHIT!
What about:
• Cache?
• What if we have a list side-by side, it is updated?
• What if we have view and update side-by-side?

SHIT!
How to solve it?
• New services?
• Callbacks?
• RxJS?
• More caches?
• Events?

WHAT IS THE REAL PROBLEM?

WHAT IS THE REAL PROBLEM?
R4 (manage caches) is hidden another responsibility:
• Single source of true
We need a model!

WHAT A MODEL IS NOT?
• A model is not styles in the web
• A model is not objects in the scope
• A model is not objects stored in the browser (local,websql,…)
• A model are not instances of any sort of data
• A model is not plain data

SINGLE SOURCE OF TRUE
WHAT IS A MODEL?
• You can find your model
• There is only one instance for each “concept” 
(all books with the same id are the same object)
• Models may be computed from other models
• It does not matters how many views do you have,  
all views use the same models 
(as do services also)
That is something that ember programmers knows very well.

REFACTOR - ADD MODEL
Book
app.value(‘Book’, function Book(id) {
this.id = id;
this.isSciFi = function() { return !!this.tags.sciFi; };
this.takeData = function(bookData) {
angular.extend(this, bookData);
};
});
We discover new responsibilities:
• R5: update and extract information of a book

booksDictionary
app.value(‘booksDictionary’, (Book) => {
this.list = []; this.map = {};
this.getOrCreate = (id) => {
var book = this.map[id];
if (!book) {
book = new Book(id);
this.list.push(book); this.list.map[id] = book;
};
return book;
};
this.takeDatas = (bookDatas) => {
bookInfos.forEach((bookData) => {
this.getOrCreate(bookData.id).takeData(bookData);
});
};
});
We discover new responsibilities:
• R6: manage book instances to avoid replicates
• R7: store books so anyone can access to them
Note that list 
is also a model.

booksService (loadAll)
app.service(‘booksService’, (booksDictionary, $http) => {
if (!this.list) {
this.list = $http.get(‘/api/v1/books’).then(response => {
booksDictionary.takeDatas(response.data);
return booksDictionary.list;
});
}
return this.list;
});
};
…
});
getList returns always the same instance of list.

booksService (load)
…
this.books = {};
if (!this.books[id]) {
this.books[id] = $http.get(‘/api/v1/books/’+id).then(response => {
var book = booksDictionary.getOrCreate(id);
book.takeData(reponse.data);
return book;
});
}
return this.books[id];
};
…
});
Load(id) returns always the same instance of book for the same id.
And the instance will be contained by the list in getList.

booksService (update)
…
var id = book.id;
this.books[id] = $http.put(‘/api/v1/books/’+id).then(response => {
book.takeData(response.data);
return book;
});
};
});
Update returns always the same instance than get and getList,
regardless the input. And also updates the same instance.

three layers
SERVICES
MODELS VIEWS
calls
updates
are $watched

DONE!

DONE?
What about Sci-Fi list?
• Is computed: 
it has to be recomputed each time that a book o list changes 
• A filter is expensive
• Watch a derive function is expensive
• Watch all books (aka $watch(,,true)) is expensive

SHIT!
Solved in the next talk…

three kinds of components
ORIGINAL MVC
CONTROLLERS
MODELS VIEWS
are listenedupdates
are observed

the truth
ORIGINAL MVC
MODELS VIEWS
knows and queries
are listenedupdates
are observed
knows and queries
CONTROLLERS

ORIGINAL MVC
SHIT!
It is not as beautiful and easy as it seems.
May be it worked in ’78, with just few Kb…
and low complexity, but now…

FB comments about MVC
ARCHITECTURES VARIATIONS
https://youtu.be/nYkdrAPrdcw?t=10m20s

“MVC works pretty well
for small applications…
but it doesn’t make room
for new features.”
“Flux is a single direction data flow,
that avoids all the arrows
going on all directions
what makes really
hard to understand the system.”

“Let’s see a real good example: FB chat”
“How we get to the point, so we were annoying our
users so much the just they wanted us to fix chat?”
“The problems here were:
• The code has no structure
• It was very imperative, that makes it fragile
• It loose a lot of the original intend behind it, its hard to tell what it tries [to do]
• Add more features only gets this code larger
• We had our most annoying chat bug happen over and over
• We were always fixing some pretty good edge case, the whole system was fragile
• …
• This code becomes more fragile with the time.
• No member of the team wanted to touch it, they wanted to jump to any other bug.”

AND COMMUNITY ALSO CONTRIBUTED…

redux

cyclejs

Key points are:
• Single direction flow
• Avoid imperative code
• Decoupled state from views
• Computed data consistency 
(example: cart.price = ∑item.price * item.quantity)

mvc
FROM MVC TO MVS
MODELS VIEWS
knows and queries
are listenedupdates
are observed
knows and queries
CONTROLLERS

mvc-angular
FROM MVC TO MVS
MODELS VIEWS
knows and queries
are $watched
CONTR
OLLERS

the same flow
FROM MVC TO MVS
SERVICES
MODELS VIEWS
calls
updates
are $watched

MVS RULES (I)
SERVICES
MODELS VIEWS
calls
updates
are $watched
• Views can call to services
• Services manages models
• Models are watched by views through $watch
• Views cannot modify models but temporary copies
• Each services has its own models and do not modify other
services models

Key points are:
• Single direction flow
• Avoid imperative code
• Decoupled state from views
• Computed data consistency 
(example: sciFiBooks = books.filter(isSciFi))
ANGULAR MVS

SOLUTION FOR SCI-FI-BOOKS
• Create a new model for SciFiBooks
• Add a method getSciFiBooks() to bookService
• Recompute the list each time that an update() method is called

BUT!

BUT!
It does not scale.
¿What happens with more kind of books?
¿What happens with more complex data?

• We need a synchronization mechanism
• ex: events or observables

SOLUTION FOR COMPUTED VALUES
MODELS
• Models launch update: ex $broadcast(‘booksChanged’)
for angular1
fire events

SOLUTION FOR COMPUTED VALUES
MODELS
• Models launch update: ex $broadcast(‘booksChanged’) 
 
 
• Rules:
• Each model has its own event (1 <-> 1)
• We do not pass any information (ex: previous and new value)
• Change event is fired by the Service that manages the model
• Events can be debounced (multiple collapsed in one)
rules
fire events

booksService (update)
app.service(‘booksService’, (booksDictionary, $http, $broadcast) => {
…
var id = book.id;
this.books[id] = $http.put(‘/api/v1/books/’+id).then(response => {
book.takeData(response.data);
$broadcast(‘booksChanged’);
return book;
});
};
});

<APP-SCI-FI-BOOKS-LIST> (update)
controller(booksService, $scope) {
getSciFiBooks();
$scope.$on(‘booksChanged’, getSciFiBooks);
function getSciFiBooks() {
});
}
},
});

controller(booksService, $scope) {
getSciFiBooks();
$scope.$on(‘booksChanged’, getSciFiBooks);
function getSciFiBooks() {
});
}
},
});
It smells to a service function…

sciFiBooksService (update)
app.service(‘sciFiBooksService’, (booksService, $rootScope) => {
this.list = [];
this.getList = () => this.list;
updateList();
$rootScope.$on(‘booksChanged’, updateList);
function updateList() {
angular.copy(books.filter(isSciFi), this.list);
$broadcast(‘sciFiChanged’);
});
}
});

controller(sciFiBooksService, $scope) {
sciFiBooksService.getList().then(books => {
this.books = books;
});
},
});

Hierarchy
book
Service
sciFiBooks
Service
is listened
calls
Main Rule: no cycles of the arrow same color

Hierarchy
product
Service
Main Rule: no cycles of the arrow same color
showroom
Service
user
Service
cart
Service
shipping
Service
payment
method
Service
addresses
Service

the same flow
MVS
SERVICES
MODELS VIEWS
calls
updates
are $watched

the same flow
MVS
SERVICES
MODELS
VIEWS
calls
updates
are $watched
Dumb
Views
Smart
Views
BROWSER
uses listens
uses listens

the same flow
MVS
SERVICES
MODELS
VIEWS
calls
updates
are $watched
Dumb
Views
Smart
Views
BROWSER
uses listens
uses listens
Services
Remotes Storages
callscalls

the same flow
MVS
SERVICES
MODELS VIEWS
calls
updates
are $watched
Dumb
Views
Smart
Views
BROWSER
uses listens
uses listens
Services
Remotes Storages
callscalls
State
Holders
State
Singletons
State
Dictionaries
CI
CI
CICICI

computed data flow
MVS
SERVICES
MODELS VIEWS
calls
updates
are $watched
Dumb
Views
Smart
Views
BROWSER
uses listens
uses listens
Services
Remotes Storages
callscalls
State
Holders
State
Singletons
State
Dictionaries
CI
CI
CICICI

computed data flow
MVS
SERVICES
MODELS VIEWS
calls
updates
are $watched
Dumb
Views
Smart
Views
BROWSER
uses listens
uses listens
Services
Remotes Storages
callscalls
State
Holders
State
Singletons
State
Dictionaries
CI
CI
CICICI
are listened
are listened

step by step
COMPUTED DATA FLOW
1. call
5. is fired
Books
Service
Books
Dictionary
Sci-Fi
Service
Sci-Fi
Dictionary
2. updates
3. fire $update
7. updates
8. fire $update
$UPDATE
EVENT MANAGER
4. fire $update
6. reads

MVS: An angular MVC

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MVS: An angular MVC