[v5] hasOne preload return error undefined in null id

[arthurcvm]

In my system I make a CRUD operation and after make a refresh followed by a preload in all related models, this was working normally for belongsTo, but in hasOne relationship return an error when the id is null, look the code:

await sector.refresh()
await sector.load((loader) => {
    loader.preload('supervisor').preload('coordinator')
      .preload('manager').preload('department')
})

The exception returned:

Exception: Cannot preload "supervisor", value of "Sector.supervisor_id" is undefined

But in belongsTo relationship this code work.
What's the problem?

[arthurcvm]

I understood the docs, in Sector I set belongsTo and in Supervisor I set hasOne, this way it works.

[d4n1b]

I had a hard time understanding this too. It's safe for null values when using the combination you mentioned.

In my case I have Activities & Clients.

This does NOT work when client_id is null ❌ :

export default class Activity extends BaseModel {
  @hasOne(() => Client)
  public client: HasOne<typeof Client>;

This DOES work when client_id is null ✅ :

export default class Activity extends BaseModel {
  @belongsTo(() => Client)
  public client: BelongsTo<typeof Client>;

[thetutlage]

For that you need to understand when to use belongsTo and when to use hasOne. In your case it should be belongsTo. A simple way to remember is.

A model that has the foreign key makes a belongs to relationship with the other model

[d4n1b]

Thanks @thetutlage - It will be definitely easier to remember now 😄👍