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Angular DI Processor Pattern
Jecelyn Yeen
September 27, 2018
Programming
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520
Angular DI Processor Pattern
Implement Processor Pattern with Angular Dependency Injection
Jecelyn Yeen
September 27, 2018
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Transcript
Angular | Dependency Injection | Processor Pattern + +
@JecelynYeen From Kuala Lumpur, Malaysia • GDE - Web technologies,
Angular • Software Architect @ Randstad Organizer:
• Dependency Injection (DI) • DI in Angular • Processor
Pattern • DI + Processor Pattern in Angular + +
Dependency Injection . What & Why?
Weapon is made of material (wood). Ninja needs a weapon
(nunchakus). We have a ninja.
- Single Responsibility - Tightly coupled - Hard to unit
test
Dependency Injection
Hookup implementation during bootstrap inject in constructor no need to
instantiate
Replace implementation under the hood
Dependency Injection • Unit testable • Reusability • Loosely coupled
• Dependency Inversion principle
DI in Angular
service service hook up
• UseClass • UseValue • UseFactory • UseExisting + https://offering.solutions/blog/articles/2018/08/17/using-useclass-usefactory-usevalue-
useexisting-with-treeshakable-providers-in-angular/ https://blog.thoughtram.io/angular/2015/05/18/dependency-injection-in-angular-2.html
Dependency Injection is static
Dependency Injection is static hook up only once
what if our ninja need to switch weapon dynamically https://di-processor.firebaseapp.com/ninja-di
what if our ninja need to switch weapon dynamically https://di-processor.firebaseapp.com/ninja-di
nunchakus, dart, stick, sword
Processor Pattern using injection token & multi-provider
weapon interface name, draw(), animate() Inject into NinjaComponent as weapon[
] injection token processors multi-providers
Injection Token + Processor Interface
Processor implement the interface
Multiple providers with same token one token multiple implementations set
as multi
Inject multiple providers Injection 4 processors get one processor Invoke
processor functions
Production Use Case: Chart Processors
- chart type - title / menu - processing logic
- labels & tooltips Differences - they are all charts - same interface:- - processData() - name, title, etc Similar https://di-processor.firebaseapp.com
YYYY-MM what users want to see YYYY-MM-DD what backend returns
Frontend developer
what your chart library wants what you need to do
• transform data (loop & group it by year month) • sort it • generate chart configuration
What you actually do - Chart Processor https://github.com/chybie/di-processor/blob/master/src/app/chart-di/services/chart-new-starter-processor.service.ts private
Injection Token + Processor Interface
Multiple providers with same token
Dashboard Component
Other useful scenario • Data table processors • Search processors
https://stackoverflow.com/questions/48382323/angular-lookup-all- providers-implementing-a-specific-interface/ 48383858#comment83773434_48383858
Benefits • Abstraction • Plugins
slides: https://speakerdeck.com/chybie/angular-di-processor-pattern demo: https://di-processor.firebaseapp.com code: https://github.com/chybie/di-processor code (inject by service):
https://stackblitz.com/edit/ninja-weapon- processors?file=src%2Fapp%2Fninja%2Fninja.component.ts twitter: @JecelynYeen + +