Loopback 4: Join 2 related models

Question

I am building a project were I have a list of jobs were each job belongs to a company.

REST controller called Job (just to make it simple) it has 2 methods:

• @get('/jobs')
• @get('/jobs/{id}')

For the case of @get('/jobs/{id}') I found a not perfect solution:

@get('/jobs/{id}', {
    responses: {
      '200': {
        description: 'Job model instance',
        content: {'application/json': {schema: {'x-ts-type': Job}}},
      },
    },
  })
  async findById(@param.path.number('id') id: number): Promise<Job> {
    const job: Job = await this.jobRepository.findById(id);
    const company: Company = await this.jobRepository.company(job.company_id);

    job.company = company;

    return job;
  }

I added a property company were I assigned the company.

But for @get('/jobs') it is not so easy, to apply similar approach I would have to loop all results to add company, but this approach it is not efficient.

Any ideas?

Answer 1

According to forums, Loopback is not able to do joins yet. It is scheduled for next 3 months though, meanwhile I solved doing:

@get('/jobs', {
    responses: {
      '200': {
        description: 'Array of Job model instances',
        content: {
          'application/json': {
            schema: {type: 'array', items: {'x-ts-type': Job}},
          },
        },
      },
    },
  })
  async find(
    @param.query.object('filter', getFilterSchemaFor(Job)) filter?: Filter,
  ): Promise<{jobs: Job[]; count: number}> {
    const jobs = await this.jobRepository.find(filter);

    await Promise.all(
      jobs.map(
        async (job): Promise<Job> => {
          let company = await this.jobRepository.company(job.company_id);
          return (job.company = company);
        },
      ),
    );

    const count = await this.jobRepository.count();

    return {jobs, ...count};
  }

If you have suggestions to improve code, let me know.