PATTERNS THAT BOOST OUR FRAMEWORKS

Laurent Wroblewski

Développeur Web / Mobile

@LaurentWrob

Why?

```
Everything is changing very fast!
```

2009...

JQuery, Tapestry, Flash, Flex, Backbone, ie...

2013...

```
AngularJS
```

2016...

```
Angular, Android
```

Today...

```
React, Stencil, Flutter, ie... :(
```

A solution?

```
Following the SOLID principles :
```

Building software designs...

```
More understandable
```
```
Easier to maintain
```
```
Easier to extend
```

```
A list of commonly used patterns ;)
```

Starting by a well known structural pattern...

1. MVC

```
A long, long time ago...
```

1. MVC

```
Angular :
```

```
View
```
```
Controller
```
```
Model
```

```
HTML Template
```
```
Component
```
```
Service
```

```
React :
```

```
View
```
```
Controller
```
```
Model
```

```
View
```

1. MVC

<div>
  <app-user-search (changed)="onCriteriaChanged($event)">
  </app-user-search>
	
  <app-users-list [users]="users$ | async" 
    (select)="onSelectUser($event)">
  </app-users-list>
</div>

```
"View"
```

1. MVC

@Component({
  templateUrl: './main-page.component.html',
  styleUrls: ['./main-page.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class MainPageComponent implements OnInit {

  users$: Observable<User[]>;

  constructor(private userService: UserService) {}

  ngOnInit() {
    this.users$ = this.userService.fetchUsers();
  }
}

```
"Controller"
```

1. MVC

@Injectable()
export class UserService {
  constructor(@Inject(USER_API_URL) private urlUsers: string,
              private http: HttpClient) {}

  fetchUsers(criteria: UserCriteria): Observable<User[]> {
    return this.http.get<User[]>(this.urlUsers);
  }
}

```
"Model"
```

1. MVC

```
Other structuring patterns :
```

```
MVP (Model - View - Presenter)
```

1. MVC

```
Other structuring patterns :
```

```
MVVM (Model - View - ViewModel)
```

1. MVC

```
MVVM Android :
```

class ViewModelActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        // Obtain the ViewModel component.
        UserModel userModel = ViewModelProviders.of(getActivity())
                                                .get(UserModel.class)

        // Inflate view and obtain an instance of the binding class.
        val binding: UserBinding = 
          DataBindingUtil.setContentView(this, R.layout.user)

        // Assign the component to a property in the binding class.
        binding.viewmodel = userModel
    }
}

1. MVC

```
MVVM Android :
```

<CheckBox
    android:id="@+id/rememberMeCheckBox"
    android:checked="@{viewmodel.rememberMe}"
    android:onCheckedChanged="@{() -> viewmodel.rememberMeChanged()}" />

2. REACTIVE PrograMMING

2. Reactive Programming

```
Asynchronous data streams
```

2. Reactive Programming

```
Everything is a stream :
```

2. Reactive Programming

Declarative approach using :

```
Pure functions
```
```
Iterator pattern
```

const products$: Observable<Product[]> = 
      fromEvent(this.input.nativeElement, 'keyup')
    .pipe(
        map(event => event.target.value),
        filter((search: String) => search.length > 2),           		
        debounceTime(250),
        distinctUntilChanged(),
        switchMap(search => this.fetchProducts(search)) 
    );

2. Reactive Programming

ReactiveX implementations :

```
RxJS
```
```
RxJava
```
```
RxKotlin
```
```
RxDart
```
```
RxPython
```
```
...
```

2. Reactive Programming

Common uses :

```
Angular HttpClient, ReactiveForms...
```
```
Android LiveData
```
```
Flutter FutureBuilder/StreamBuilder
```
...

2. Reactive Programming

```
Heavily depends on...
```

Observer pattern

3. OBSERVER

3. Observer

```
Event handling :
```

```
Observers
```
```
Subjects
```

3. Observer

```
Event handling :
```

3. Observer

```
Subject :
```

```
Observer :
```

```
registerObserver(observer)
```
```
unregisterObserver(observer)
```
```
notifyObservers()
```

```
notify()
```

3. Observer

```
Main goal :
```

Separation of concerns

4. SINGLETON

4. Singletons

```
Single instance
```
```
Coordinate actions across the system
```
```
Perfect to store data
```
```
Lazy construction
```

4. Singletons

Angular Services

```
Business specific
```
```
Transverse
```

@Injectable()
export class UserService {

  constructor(@Inject(USER_API_URL) private urlUsers: string,
              private http: HttpClient) {}

  fetchUsers(): Observable<User[]> {
    return this.http.get<User[]>(this.urlUsers);
  }
}

4. Singletons

Angular Services

```
Easy to use...
```
```
Thanks to Dependency Injection
```

@Component({
  templateUrl: './detail-page.component.html',
  styleUrls: ['./detail-page.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class DetailPageComponent implements OnInit {

  users$: Observable<User[]>;

  constructor(private userService: UserService) {}

  ngOnInit() {
    this.users$ = this.userService.fetchUsers();
  }

4. Singletons

Angular Services

```
Best place to store business data
```

@Injectable()
export class UserService {

  private _users$: Observable<User[]>;

  get users$(): Observable<User[]> {
    return this._users$;
  }

  constructor(@Inject(USER_API_URL) private urlUsers: string,
              private http: HttpClient) {
    this._users$ = this.http.get<User[]>(this.urlUsers).pipe(
      shareReplay()
    );
  }
}

4. Singletons

```
Redux Store
```

4. Singletons

⚠️ Warning ⚠️

```
Testability
```
```
Dependency hiding
```
```
Concurrency
```

5. FACTORY

```
Creational pattern
```

One interface and several implementations

Using the Right implementation for a given case

5. FACTORY

Generally used with a DI mechanism :

```
Angular services
```
```
Android libraries (Dagger 2, Koin)
```
```
Flutter libraries (Inject)
```

5. FACTORY

```
Angular Injection Tokens :
```

// user.service.ts
export const USER_SERVICE = 
       new InjectionToken<UserService>('USER_SERVICE');

export interface UserService {
  fectchAll(): Observable<User[]>;
  fectchOne(): Observable<User>;
}

5. FACTORY

```
Angular module :
```

// app.module.ts
@NgModule({
  declarations: [AppComponent],
  imports: [
    ...
  ],
  providers: [
    { provide: USER_SERVICE, useClass: UserServiceHttpImpl },
    ...
  ],
  bootstrap: [AppComponent]
})
export class AppModule {}

5. FACTORY

```
Angular Environments
```

// app.module.ts
@NgModule({
  ...
  providers: [
    { provide: USER_SERVICE, useClass: environment.userServiceImpl },
    ...
  ]
})
export class AppModule {}

// environment.ts
{
  userServiceImpl: UserServiceHttpImpl
}

6. STRATEGY

```
Encapsulates a family of algorithms
```
```
Makes them interchangeable.
```

6. STRATEGY

In a component architecture :

```
Dumb - Smart components
```
Presentational - Container components

// detail-page.component.ts
<div class="user-detail-content" *ngIf="user$ | async as user">
  <h1>{{ user.firstName }}</h1>
  <app-user-form [user]="user" (validate)="onValidate($event)">
  </app-user-form>
</div>

7. DECLARATIVE UI

7. Declarative UI

```
The new standard in front development?
```

```
Declarative API to define UI components
```

export default class App extends Component {

  ...

  render() {
    return (
      <div>
        <Header />
        <List items={this.state.items} />
        <Footer />
      </div>
    );
  }
}

7. Declarative UI

```
More than just "UI" components :
```

@override
Widget build(BuildContext context) => FutureBuilder<Restaurant>(
  future: restaurantService
    .fetchRestaurantDetail(context: context, restaurant: restaurant)
    .then((restaurant) => restaurantService.fetchRestaurantRatings(
       restaurant: restaurant,
       limit: 4
      )),
  builder: (context, snapshot) {
    if (snapshot.hasError) print(snapshot.error);
    return snapshot.hasData
      ? RestaurantWidget(restaurant: snapshot.data)
      : AppProgressIndicator();
 });

7. Declarative UI

At last on Android :

```
Android Jetpack Compose 
```

class ComposeActivity : Activity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent { CraneWrapper { MyApp() } }
    }

    @Composable
    fun MyApp() {
        MaterialTheme {
            Text(
              text = "Hello world!", 
              style = +themeTextStyle { h3 }
            )
        }
    }
}

Question :

I have developed a components library and want to implement a "disabled" and "tabIndex" state on all of them... ?

8. MIXIN

Solves a common Class limitation :

```
Single Super Class
```

Share a common behavior between different classes

8. MIXIN

```
Mixins can be done in Typescript
```
```
But it can be a bit tricky
```

Used in some component libraries (Angular Material) to define common behavior such as "color", "disabled"...

8. MIXIN

```
Well implemented in Dart 2.X :
```

mixin Coder {
  void code() {
    print("Trying to use design patterns...");
  }
}

class Laurent extends Person with Coder {}

void main() {
  const laurent = Laurent();
  laurent.code();
}

8. MIXIN

With interface default implementations in Kotlin :

interface Developer {

  fun code() {
    ...
  }
}

class UserCodeEnSeine : User, Developper {
  ...
}

8. MIXIN

```
React hooks are Mixins done right :
```

function Example() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Vous avez cliqué {count} fois</p>
      <button onClick={() => setCount(count + 1)}>
        Cliquez ici
      </button>
    </div>
  );
}

conclusion

To conclude...

```
Patterns are the first thing to learn.
```

Frameworks use them to solve common software development problems.

Their implementation differs, but the logic remains the same.

PATTERNS THAT BOOST OUR FRAMEWORKS

Laurent Wroblewski

Développeur Web / Mobile

Why?

2009...

2013...

2016...

Today...

A solution?

A solution?

Contents

1. MVC

1. MVC

1. MVC

1. MVC

1. MVC

1. MVC

1. MVC

1. MVC

1. MVC

1. MVC

1. MVC

2. REACTIVE PrograMMING

2. Reactive Programming

2. Reactive Programming

2. Reactive Programming

2. Reactive Programming

2. Reactive Programming

2. Reactive Programming

Observer pattern

3. OBSERVER

3. Observer

3. Observer

3. Observer

3. Observer

Separation of concerns

4. SINGLETON

4. Singletons

4. Singletons

4. Singletons

4. Singletons

4. Singletons

4. Singletons

⚠️ ​Warning ⚠️

5. FACTORY

5. FACTORY

5. FACTORY

5. FACTORY

5. FACTORY

5. FACTORY

6. STRATEGY

6. STRATEGY

6. STRATEGY

7. DECLARATIVE UI

7. Declarative UI

7. Declarative UI

7. Declarative UI

Question :

8. MIXIN

8. MIXIN

8. MIXIN

8. MIXIN

8. MIXIN

8. MIXIN

conclusion

To conclude...

THANKS! 🙏

⚠️ Warning ⚠️