villar

Villar factory

Facilitates factory creation and infrastructure

Usage

---

Classes and decorators

1. Implementation

   1. key defines which key the impl represents
   2. implName if the instance is initialized with the original class name
   3. ref distinguishes if there are two identical keys for different implementations

2. VillarImplDiscovery

   1. findImpl(string) searches for the implementation according to the key provided

3. NestVillarImplDiscovery

   1. findImpl(string) has the same function as VillarImplDiscovery but does search for impl in the context of nest injection

Usage example

Configurate the impls

// The interface
export interface Calculator {
    calc(num1: number, num2: number): number
}

import { Implementation } from "villar"

// Addition impl
@Implementation({
    key: '+'
})
// At NestJs use @Injectable()
export class AdditionCalculator implements Calculator {

    calc(num1: number, num2: number): number {
        return num1 + num2
    }

}

// Subtraction
@Implementation({
    key: '-'
})
// At NestJs use @Injectable()
export class SubtractionCalculator implements Calculator {

    calc(num1: number, num2: number): number {
        return num1 - num2
    }
}

// Division
// includes attr is like in key
@Implementation({
    key: 'any_division_inclues(/)',
    includes: true
})
export class DivisionCalculator implements Calculator {

    calc(num1: number, num2: number): number {
        return num1 / num2
    }

}

// Multiplication
// truthCustom is function from custom truth impl selector
// function (key: string, metadata: any)
@Implementation({
    key: 'multiplication*',
    truthCustom: (key: string, metadata: any): boolean => { 
        return key.includes('*') && metadata?.value == 10
    }
})
export class MultiplicationCalculator implements Calculator {

    calc(num1: number, num2: number): number {
        return num1 * num2
    }

}

Discovery impls

import { VillarImplResolver } from "villar"

// Register impls
VillarImplResolver.register(SubtractionCalculator, AdditionCalculator)

// Addition Impl
const calculator: Calculator | undefined = VillarImplDiscovery.getInstance().findImpl<Calculator>('+')
console.log(calculator?.calc(10, 1)) //result: 11

// Subtraction Impl result
const calculator: Calculator | undefined = VillarImplDiscovery.getInstance().findImpl<Calculator>('-')
console.log(calculator?.calc(10, 1)) //result: 9

// Anu Impl rsult
const calculator: Calculator | undefined = VillarImplDiscovery.getInstance().findImpl<Calculator>('any_key')
console.log(calculator?.calc(10, 1)) //result: undefined

// Division
const calculator: Calculator | undefined = VillarImplDiscovery.getInstance().findImpl<Calculator>('*')
console.log(calculator?.calc(10, 2)) //result: 5

// Multiplication
const options: any = { 
      metadata: { 
        value: 10 
      }
    }

const calculator: Calculator | undefined = VillarImplDiscovery.getInstance().findImpl<Calculator>('*',  options)
console.log(calculator?.calc(10, 2)) //result: 20

NestJs Discovery impls

// Configure AppModule
@Module({
  imports: [],
  controllers: [AppController],
  providers: [
    AdditionCalculator, // Custom impl
    SubtractionCalculator // Custom impl,
    NestVillarImplDiscovery, // Helper Villar, import with import { NestVillarImplDiscovery } from "villar",
    anysProviders....
  ],
})
export class AppModule {}

// Example in controller

@Controller()
export class AppController {
  
  constructor(
    private readonly implDiscovery: NestVillarImplDiscovery
  ) {}

  @Get("execute-calc/:operator/:value/:value2")
  executeCalc(@Param("operator") operator: string, @Param("value") value: number, @Param("value2") value2: number) {
    const calculator = this.implDiscovery.findImpl<Calculator>(operator)
    return calculator?.calc(value, value2)
  }
}