How do I update an relation?

[tarjei]

Hi, how do I update a relationship?

I.e if I want to add an extra entry to an existing manyOf relationship.

Example code:

{
post: {
    id: primaryKey(() => faker.unique(faker.datatype.number)),
    title: faker.datatype.string,
   images: nullable(manyOf('image')),
  },
image: {
   id: primaryKey(() => faker.unique(faker.datatype.number)),
url: faker.datatype.string
}
}

In an msw rest handler I got something like this:

rest.post('/api/images', (req, res, ctx) => {
  
  const postId = parseInt(req.body.get('postId'),10)
  const image = db.image.create({url: req.body.get('url')})
  
  
  const post = db.post.findFirst({...})
  post.images.push(image)
  db.post.update({
    where: {id: {equals: postId}},
    data: {
       images: post.images
    }
  })
}

I'm sure there is something haven't understood. How can I ensure that the image gets added to posts.images ?

[kettanaito]

Hi, @tarjei.

Here's how you can update a manyOf relation by pushing a new entity to the relational value:

const db = factory({
  post: {
    id: primaryKey(String),
    images: manyOf('image')
  },
  image: {
    id: primaryKey(String),
    url: String
  }
})

rest.post('/api/images', (req, res, ctx) => {
  // Create a new "image" entity.
  const newImage = db.image.create({
    url: req.body.url
  })

  // Update a certain post(s) by adding a new image
  // to the existing "post.images" relationship.
  const nextPost = db.post.update({
    where: { id: { equals: 'some-post' } },
    data: {
      images(prevImages) {
        // Grab the previous value of "post.images"
        // and add the newly created post to it.
        return prevImages.concat(newImage)
      }
    }
  })

  // Optionally, consider concluding with a HTTP response.
  return res(ctx.status(201), ctx.json(newImage)))
})

The main point here is that each property in the data of update/updateMany can also accept a function. That function is called as follows:

data/src/model/updateEntity.ts

Line 38 in df18b9d

typeof value === 'function' ? value(prevValue, entity) : value

So it accepts the previous value of this particular property (post.images in this case of the particular post that you're updating) and the entire entity (post in this case).

[tarjei]

Thank you for this great answer @kettanaito