# Models

The `models` root folder contains all the model files, i.e. files containing all the models. **Models** here, refers to the classes that handle the data, its validation and updation and a bunch of other stuff.

Each model directly or indirectly extends the `Doc` class from `frappe/model/doc.ts` so for more info check that file and the associated types in `frappe/model/types.ts`.

A model class can used even if the class body has no content, for example `PurchaseInvoiceItem`. Else the model used will default to using `Doc`. The class can also be used to provide type information for the field types else they default to the catch all `DocValue` example:

```typescript
class Todo extends Doc {
  title?: string;
  date?: Date;
  completed?: boolean;
}
```

While this has obvious advantages, the drawback is if the underlying fieldtype changes this too will have to be changed.

## Adding Stuff

When adding stuff to `models/**` make sure that it isn't importing any Vue code or other frontend specific code globally. This is cause model file tests will directly use the the `Frappe` class and will be run using `mocha` on `node`.

Importing frontend code will break all the tests. This also implies that one should be wary about transitive dependencies.

_Note: Frontend specific code can be imported but they should be done so, only using dynamic imports i.e. `await import('...')`._

## Regional Models

Regional models should as far as possible extend the base model and override what's required.

They should then be imported dynamicall and returned from `getRegionalModels` in `models/index.ts` on the basis of `countryCode`.