Selecting logic depending on the request body in NestJS

Question

Selecting logic depending on the request body in NestJS

Currently, my controller looks like the following:

@Controller("workflow")
export class TaskWorkflowController {
  public constructor(
    private readonly jobApplicationActivityWorkflow: JobApplicationActivityService
  ) {}

  @Post("/:job-application-activity")
  public startWorkflow(
    @Body() body: StartJobApplication | StartJobActivity,
    @Param("job-application-activity") jobApplicationActivity: string
  ): void {
    switch (jobApplicationActivity) {
      case "job-application":
        return this.jobApplication.execute(body);
      case "job-activity":
        return this.jobActivity.execute(body);
      default:
        throw new Error("Invalid workflow");
    }
  }

The scenario I am facing is triggering different logic based on the job-application-activity parameter. The issue arises from having a body of type

StartJobApplication | StartJobActivity

, while my services are of type StartJobApplication and StartJobActivity.

How can I address this complication?

typescript express controller nestjs

Answer 1

Answer №1

One challenge you may encounter is the inability to perform validation because Typescript does not accurately represent the union type. However, if this limitation is not a deal-breaker for you, consider implementing a type guard instead of a switch statement. You can achieve this by:

@Controller("workflow")
export class TaskWorkflowController {
  public constructor(
    private readonly jobApplicationActivityWorkflow: JobApplicationActivityService
  ) {}

  @Post("/:job-application-activity")
  public startWorkflow(
    @Body() body: StartJobApplication | StartJobActivity,
    @Param("job-application-activity") jobApplicationActivity: string
  ): void {
    if (jobApplicationActivity.propertyOnlyOnStartJobApplication) {
        return this.jobApplication.execute(body);
    } else if(jobApplicationActivity.propertyOnlyOnStartJobActivity)
        return this.jobActivity.execute(body);
    } else {
        throw new Error("Invalid workflow");
    }
  }
}

Answer 2

One challenge you may encounter is the inability to perform validation because Typescript does not accurately represent the union type. However, if this limitation is not a deal-breaker for you, consider implementing a type guard instead of a switch statement. You can achieve this by:

@Controller("workflow")
export class TaskWorkflowController {
  public constructor(
    private readonly jobApplicationActivityWorkflow: JobApplicationActivityService
  ) {}

  @Post("/:job-application-activity")
  public startWorkflow(
    @Body() body: StartJobApplication | StartJobActivity,
    @Param("job-application-activity") jobApplicationActivity: string
  ): void {
    if (jobApplicationActivity.propertyOnlyOnStartJobApplication) {
        return this.jobApplication.execute(body);
    } else if(jobApplicationActivity.propertyOnlyOnStartJobActivity)
        return this.jobActivity.execute(body);
    } else {
        throw new Error("Invalid workflow");
    }
  }
}

Selecting logic depending on the request body in NestJS

Answer №1

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