docs: update Models.md

[agnes512]

clean up old content and make it less relate to lb3
some content are copied from lb3 and rewrite it with lb4-way

closes loopbackio/loopback.io#907

While doing ^907, I realized that we link to LB3 docs a lot. Considering there are several differences between them and not all users are familiar with LB3, I think it's time to separate them. ( And ofc it is also annoying to jump back and forth between LB3 and LB4 docs)

So I edited the Model Decorator and Property Decorator sections that:

• copy content form LB3 if we linked it to LB3 before.
• Remove the unsupported part and rewrite it with Ts-way to LB4.
• Edit them as a whole to make it more consistent

I tested them briefly before I removing some features/entries. If you happen to know that they are still available but got deleted, please kindly let me know, thanks!!

Checklist

👉 Read and sign the CLA (Contributor License Agreement) 👈

• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

👉 Check out how to submit a PR 👈

[jannyHou]

👍 LGTM in general good update! a few nitpicks.
I think lb3 uses scopes instead of scope?

[jannyHou]

Suggested change

	### Scope
	### Scopes

[jannyHou]

The field name is in plural :p https://loopback.io/doc/en/lb3/Model-definition-JSON-file.html#scopes

[agnes512]

Yes, but in LB4 it only works with settings scope:

@model({
  settings: {
    scope: {
      'limit': 2,
    },
    idInjection: true
  }
})

:( that's why I made them scope instead of scopes

[jannyHou]

I see! remembered, LB3 supports both scopes and scope:

• scopes: a collection of predefined scopes
• scope: the default scope

So your change makes perfect sense 💯

[jannyHou]

Suggested change

	scope: {
	scopes: {

[jannyHou]

And I think you need to give each scope a name?
Like

"scopes": {
	"vips": {"where": {"vip": true}}, 
	"top5": {"limit": 5, "order": "age"}
}

[agnes512]

I don't think this part works in LB4, at least from what I tried.

[jannyHou]

👍 take my comment back :p

[agnes512]

Just want to double check this part: in LB3 we allow:

"scopes": {
	"vips": {"where": {"vip": true}}, 
	"top5": {"limit": 5, "order": "age"}
}

then the scopes can be used as

User.scope("vips", { where: { vip: true } });
User.scope("top5", { limit: 5, order: "age" });

I don't think this is valid in LB4 because:

• User model, or any lb4 model, doesn't have such method scope
• LB4 uses repositories to query data. So User.scope won't work.

Is this correct?

[jannyHou]

Defining

"scopes": {
	"vips": {"where": {"vip": true}}, 
	"top5": {"limit": 5, "order": "age"}
}

is equivalent to

// please note User.scope defines scope, not apply scope
User.scope("vips", { where: { vip: true } });
User.scope("top5", { limit: 5, order: "age" });

After defining them, you can call APIs like User.vips() to query with the predefined filter.

But your conclusion is correct 👌 we don't have such APIs in User repository. Therefore scopes won't be supported. Only specifying the default scope works.

[agnes512]

Enhanced the docs for required and default fields that we discussed in #3058 in commit 685361a

[jannyHou]

💯 LGTM

[nabdelgadir]

Great work 👏

[agnes512]

Even the settings can be imported from LB3, see https://github.com/strongloop/loopback-next/pull/4737/files#r383816292, I've decided to remove idInjection. Because even the DB would have an id property added to the model automatically with idInjection: true set, the id property is still needed in the model definition so that the repository/controller can be set afterwards.

We can revert the change if ^ the conclusion is incorrect.