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2.2 Service

Services are invoked by Controller handlers to perform more complex business logic not directly related to client communication.

Query an External Service

Let’s build a simple web service that returns the latest version of some popular softtware packages as JSON. As in the previous section, we’ll create a Controller that handles the client request/response. We’ll additionally create a Service that the Controller will invoke to query the version of a package.

fab controller VersionController

fab service VersionService

Implement the Controller

// api/controller/VersionController.ts
import { FabrixController as Controller } from '@fabrix/fabrix/dist/common'

export class VersionController extends Controller {

  /**
   * Return the latest version of a given software package
   * @param request.params.packageName
   */
  getLatest (request, reply) {
    const { packageName }  = request.params

    this.services.VersionService.getLatest(packageName)
      .then(version => {
        return reply({
          [packageName]: `v${version}`
        })
      })
      .catch(err => reply(err))
  }
}

Implement the Service

VersionService will request version information from semver.io, an external web service that hosts version information on nodejs, npm, yarn, and other tools. Separating out this business logic from the request-handling duties of the Controller is a good practice for separating concerns and organizing code.

// api/services/VersionService.ts
import { FabrixService as Service } from '@fabrix/fabrix/dist/common'
import * as request from 'request-promise'

export class VersionService extends Service {

  static get supportedPackages () {
    return [
      'node',
      'npm',
      'yarn',
      'nginx'
    ]
  }

  /**
   * Query the semver.io service for the latest version of a specified package name
   * @param packageName
   */
  getLatest (packageName) {
    if (!VersionService.supportedPackages.find(packageName)) {
      throw new Error(`${packageName} not supported`)
    }

    return request(`semver.io/${packageName}`)
  }
}

Configure the Route

// config/routes.ts
export const routes = {
  '/version/{packageName}': {
    'GET': {
      handler: 'VersionController.getLatest'
    }
  }
}

Try it!

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