npm package: @gulibs/sequelize-typescript
Description: Decorators and some other features for sequelize
Author: Robin Buschmann
Latest version: 0.0.1

# sequelize-typescript

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Decorators and some other features for sequelize (v6).

- [Installation](#installation)
- [Model Definition](#model-definition)
  - [`@Table` API](#table-api)
  - [`@Column` API](#column-api)
- [Usage](#usage)
  - [Configuration](#configuration)
  - [globs](#globs)
  - [Model-path resolving](#model-path-resolving)
- [Model association](#model-association)
  - [One-to-many](#one-to-many)
  - [Many-to-many](#many-to-many)
  - [One-to-one](#one-to-one)
  - [`@ForeignKey`, `@BelongsTo`, `@HasMany`, `@HasOne`, `@BelongsToMany` API](#foreignkey-belongsto-hasmany-hasone-belongstomany-api)
  - [Generated getter and setter](#type-safe-usage-of-auto-generated-functions)
  - [Multiple relations of same models](#multiple-relations-of-same-models)
- [Indexes](#indexes)
  - [`@Index` API](#index)
  - [`createIndexDecorator()` API](#createindexdecorator)
- [Repository mode](#repository-mode)
  - [How to enable repository mode?](#how-to-enable-repository-mode)
  - [How to use repository mode?](#how-to-use-repository-mode)
  - [How to use associations with repository mode?](#how-to-use-associations-with-repository-mode)
  - [Limitations of repository mode](#limitations-of-repository-mode)
- [Model validation](#model-validation)
- [Scopes](#scopes)
- [Hooks](#hooks)
- [PostgreSQL Alter Helper](#postgresql-alter-helper)
- [Why `() => Model`?](#why---model)
- [Recommendations and limitations](#recommendations-and-limitations)

## Installation

- this assumes usage of `sequelize@6`
- _sequelize-typescript_ requires [sequelize](https://github.com/sequelize/sequelize)
- additional typings as documented [here](https://sequelize.org/master/manual/typescript.html) and [reflect-metadata](https://www.npmjs.com/package/reflect-metadata)

```sh
npm install --save-dev @types/node @types/validator
npm install sequelize reflect-metadata sequelize-typescript
```

Your `tsconfig.json` needs the following flags:

```json
"target": "es6", // or a more recent ecmascript version
"experimentalDecorators": true,
"emitDecoratorMetadata": true
```

### Sequelize Options

- `SequelizeConfig` renamed to `SequelizeOptions`
- `modelPaths` property renamed to `models`

### Scopes Options

The `@Scopes` and `@DefaultScope` decorators now take lambda's as options

```ts
@DefaultScope(() => ({...}))
@Scopes(() => ({...}))
```

instead of deprecated way:

```ts
@DefaultScope({...})
@Scopes({...}))
```

## Model definition

```typescript
import { Table, Column, Model, HasMany } from 'sequelize-typescript';

@Table
class Person extends Model {
  @Column
  name: string;

  @Column
  birthday: Date;

  @HasMany(() => Hobby)
  hobbies: Hobby[];
}
```

### Less strict

```typescript
import { Table, Model } from 'sequelize-typescript';

@Table
class Person extends Model {}
```

### More strict

```typescript
import { Optional } from 'sequelize';
import { Table, Model } from 'sequelize-typescript';

interface PersonAttributes {
  id: number;
  name: string;
}

interface PersonCreationAttributes extends Optional<PersonAttributes, 'id'> {}

@Table
class Person extends Model<PersonAttributes, PersonCreationAttributes> {}
```

The model needs to extend the `Model` class and has to be annotated with the `@Table` decorator. All properties that
should appear as a column in the database require the `@Column` annotation.

See more advanced example [here](https://github.com/RobinBuschmann/sequelize-typescript-example).

### `@Table`

The `@Table` annotation can be used without passing any parameters. To specify some more define options, use
an object literal (all [define options](https://sequelize.org/v5/manual/models-definition.html#configuration)
from sequelize are valid):

```typescript
@Table({
  timestamps: true,
  ...
})
class Person extends Model {}
```

#### Table API

| Decorator                        | Description                                                                                                                                                                                                            |
| -------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `@Table`                         | sets `options.tableName=<CLASS_NAME>` and `options.modelName=<CLASS_NAME>` automatically                                                                                                                               |
| `@Table(options: DefineOptions)` | sets [define options](https://sequelize.org/v5/manual/models-definition.html#configuration) (also sets `options.tableName=<CLASS_NAME>` and `options.modelName=<CLASS_NAME>` if not already defined by define options) |

#### Primary key

A primary key (`id`) will be inherited from base class `Model`. This primary key is by default an `INTEGER` and has
`autoIncrement=true` (This behaviour is a native sequelize thing). The id can easily be overridden by marking another
attribute as primary key. So either set `@Column({primaryKey: true})` or use `@PrimaryKey` together with `@Column`.

#### `@CreatedAt`, `@UpdatedAt`, `@DeletedAt`

Annotations to define custom and type safe `createdAt`, `updatedAt` and `deletedAt` attributes:

```typescript
  @CreatedAt
  creationDate: Date;

  @UpdatedAt
  updatedOn: Date;

  @DeletedAt
  deletionDate: Date;
```

| Decorator    | Description                                                            |
| ------------ | ---------------------------------------------------------------------- |
| `@CreatedAt` | sets `timestamps=true` and `createdAt='creationDate'`                  |
| `@UpdatedAt` | sets `timestamps=true` and `updatedAt='updatedOn'`                     |
| `@DeletedAt` | sets `timestamps=true`, `paranoid=true` and `deletedAt='deletionDate'` |

### `@Column`

The `@Column` annotation can be used without passing any parameters. But therefore it is necessary that
the js type can be inferred automatically (see [Type inference](#type-inference) for details).

```typescript
  @Column
  name: string;
```

If the type cannot or should not be inferred, use:

```typescript
import {DataType} from 'sequelize-typescript';

  @Column(DataType.TEXT)
  name: string;
```

Or for a more detailed column description, use an object literal
(all [attribute options](https://sequelize.org/v5/manual/models-definition.html#configuration)
from sequelize are valid):

```typescript
  @Column({
    type: DataType.FLOAT,
    comment: 'Some value',
    ...
  })
  value: number;
```

#### Column API

| Decorator                            | Description                                                                                               |
| ------------------------------------ | --------------------------------------------------------------------------------------------------------- |
| `@Column`                            | tries to infer [dataType](https://sequelize.org/v5/manual/models-definition.html#data-types) from js type |
| `@Column(dataType: DataType)`        | sets [dataType](https://sequelize.org/v5/manual/models-definition.html#data-types) explicitly             |
| `@Column(options: AttributeOptions)` | sets [attribute options](https://sequelize.org/v5/manual/models-definition.html#configuration)            |

#### _Shortcuts_

If you're in love with decorators: _sequelize-typescript_ provides some more of them. The following decorators can be
used together with the @Column annotation to make some attribute options easier available:

| Decorator                         | Description                                      | Options                                                                                                                          |
| --------------------------------- | ------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------- |
| `@AllowNull(allowNull?: boolean)` | sets `attribute.allowNull` (default is `true`)   |
| `@AutoIncrement`                  | sets `attribute.autoIncrement=true`              |
| `@Unique(options? UniqueOptions)` | sets `attribute.unique=true`                     | [UniqueOptions](https://github.com/sequelize/sequelize-typescript/blob/master/src/model/column/column-options/unique.ts#L3) |
| `@Default(value: any)`            | sets `attribute.defaultValue` to specified value |
| `@PrimaryKey`                     | sets `attribute.primaryKey=true`                 |
| `@Comment(value: string)`         | sets `attribute.comment` to specified string     |
| Validate annotations              | see [Model validation](#model-validation)        |

### Type inference

The following types can be automatically inferred from javascript type. Others have to be defined explicitly.

| Design type | Sequelize data type |
| ----------- | ------------------- |
| `string`    | `STRING`            |
| `boolean`   | `BOOLEAN`           |
| `number`    | `INTEGER`           |
| `bigint`    | `BIGINT`            |
| `Date`      | `DATE`              |
| `Buffer`    | `BLOB`              |

### Accessors

Get/set accessors do work as well

```typescript
@Table
class Person extends Model {
  @Column
  get name(): string {
    return 'My name is ' + this.getDataValue('name');
  }

  set name(value: string) {
    this.setDataValue('name', value);
  }
}
```

## Usage

Except for minor variations _sequelize-typescript_ will work like pure sequelize.
(See sequelize [docs](https://docs.sequelizejs.com/manual/tutorial/models-usage.html))

### Configuration

To make the defined models available, you have to configure a `Sequelize` instance from `sequelize-typescript`(!).

```typescript
import { Sequelize } from 'sequelize-typescript';

const sequelize = new Sequelize({
  database: 'some_db',
  dialect: 'sqlite',
  username: 'root',
  password: '',
  storage: ':memory:',
  models: [__dirname + '/models'], // or [Player, Team],
});
```

Before you can use your models you have to tell sequelize where they can be found. So either set `models` in the
sequelize config or add the required models later on by calling `sequelize.addModels([Person])` or
`sequelize.addModels([__dirname + '/models'])`:

```typescript
sequelize.addModels([Person]);
sequelize.addModels(['path/to/models']);
```

### globs

```typescript
import {Sequelize} from 'sequelize-typescript';

const sequelize =  new Sequelize({
        ...
        models: [__dirname + '/**/*.model.ts']
});
// or
sequelize.addModels([__dirname + '/**/*.model.ts']);
```

#### Model-path resolving

A model is matched to a file by its filename. E.g.

```typescript
// File User.ts matches the following exported model.
export class User extends Model {}
```

This is done by comparison of the filename against all exported members. The
matching can be customized by specifying the `modelMatch` function in the
configuration object.

For example, if your models are named `user.model.ts`, and your class is called
`User`, you can match these two by using the following function:

```typescript
import {Sequelize} from 'sequelize-typescript';

const sequelize =  new Sequelize({
  models: [__dirname + '/models/**/*.model.ts']
  modelMatch: (filename, member) => {
    return filename.substring(0, filename.indexOf('.model')) === member.toLowerCase();
  },
});
```

For each file that matches the `*.model.ts` pattern, the `modelMatch` function
will be called with its exported members. E.g. for the following file

```TypeScript
//user.model.ts
import {Table, Column, Model} from 'sequelize-typescript';

export const UserN = 'Not a model';
export const NUser = 'Not a model';

@Table
export class User extends Model {

  @Column
  nickname: string;
}
```

The `modelMatch` function will be called three times with the following arguments.

```text
user.model UserN -> false
user.model NUser -> false
user.model User  -> true (User will be added as model)
```

Another way to match model to file is to make your model the default export.

```TypeScript
export default class User extends Model {}
```

> ⚠️ When using paths to add models, keep in mind that they will be loaded during runtime. This means that the path
> may differ from development time to execution time. For instance, using `.ts` extension within paths will only work
> together with [ts-node](https://github.com/TypeStrong/ts-node).

### Build and create

Instantiation and inserts can be achieved in the good old sequelize way

```typescript
const person = Person.build({ name: 'bob', age: 99 });
person.save();

Person.create({ name: 'bob', age: 99 });
```

but _sequelize-typescript_ also makes it possible to create instances with `new`:

```typescript
const person = new Person({ name: 'bob', age: 99 });
person.save();
```

### Find and update

Finding and updating entries does also work like using native sequelize. So see sequelize
[docs](https://docs.sequelizejs.com/manual/tutorial/models-usage.html) for more details.

```typescript
Person.findOne().then((person) => {
  person.age = 100;
  return person.save();
});

Person.update(
  {
    name: 'bobby',
  },
  { where: { id: 1 } }
).then(() => {});
```

## Model association

Relations can be described directly in the model by the `@HasMany`, `@HasOne`, `@BelongsTo`, `@BelongsToMany`
and `@ForeignKey` annotations.

### One-to-many

```typescript
@Table
class Player extends Model {
  @Column
  name: string;

  @Column
  num: number;

  @ForeignKey(() => Team)
  @Column
  teamId: number;

  @BelongsTo(() => Team)
  team: Team;
}

@Table
class Team extends Model {
  @Column
  name: string;

  @HasMany(() => Player)
  players: Player[];
}
```

That's all, _sequelize-typescript_ does everything else for you. So when retrieving a team by `find`

```typescript
Team.findOne({ include: [Player] }).then((team) => {
  team.players.forEach((player) => console.log(`Player ${player.name}`));
});
```

the players will also be resolved (when passing `include: Player` to the find options)

### Many-to-many

```typescript
@Table
class Book extends Model {
  @BelongsToMany(() => Author, () => BookAuthor)
  authors: Author[];
}

@Table
class Author extends Model {
  @BelongsToMany(() => Book, () => BookAuthor)
  books: Book[];
}

@Table
class BookAuthor extends Model {
  @ForeignKey(() => Book)
  @Column
  bookId: number;

  @ForeignKey(() => Author)
  @Column
  authorId: number;
}
```

#### Type safe _through_-table instance access

To access the _through_-table instance (instanceOf `BookAuthor` in the upper example) type safely, the type
need to be set up manually. For `Author` model it can be achieved like so:

```ts
  @BelongsToMany(() => Book, () => BookAuthor)
  books: Array<Book & {BookAuthor: BookAuthor}>;
```

### One-to-one

For one-to-one use `@HasOne(...)`(foreign key for the relation exists on the other model) and
`@BelongsTo(...)` (foreign key for the relation exists on this model)

### `@ForeignKey`, `@BelongsTo`, `@HasMany`, `@HasOne`, `@BelongsToMany` API

| Decorator                                                                                                                     | Description                                                                                                                                                                                                    |
| ----------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `@ForeignKey(relatedModelGetter: () => typeof Model)`                                                                         | marks property as `foreignKey` for related class                                                                                                                                                               |
| `@BelongsTo(relatedModelGetter: () => typeof Model)`                                                                          | sets `SourceModel.belongsTo(RelatedModel, ...)` while `as` is key of annotated property and `foreignKey` is resolved from source class                                                                         |
| `@BelongsTo(relatedModelGetter: () => typeof Model, foreignKey: string)`                                                      | sets `SourceModel.belongsTo(RelatedModel, ...)` while `as` is key of annotated property and `foreignKey` is explicitly specified value                                                                         |
| `@BelongsTo(relatedModelGetter: () => typeof Model, options: AssociationOptionsBelongsTo)`                                    | sets `SourceModel.belongsTo(RelatedModel, ...)` while `as` is key of annotated property and `options` are additional association options                                                                       |
| `@HasMany(relatedModelGetter: () => typeof Model)`                                                                            | sets `SourceModel.hasMany(RelatedModel, ...)` while `as` is key of annotated property and `foreignKey` is resolved from target related class                                                                   |
| `@HasMany(relatedModelGetter: () => typeof Model, foreignKey: string)`                                                        | sets `SourceModel.hasMany(RelatedModel, ...)` while `as` is key of annotated property and `foreignKey` is explicitly specified value                                                                           |
| `@HasMany(relatedModelGetter: () => typeof Model, options: AssociationOptionsHasMany)`                                        | sets `SourceModel.hasMany(RelatedModel, ...)` while `as` is key of annotated property and `options` are additional association options                                                                         |
| `@HasOne(relatedModelGetter: () => typeof Model)`                                                                             | sets `SourceModel.hasOne(RelatedModel, ...)` while `as` is key of annotated property and `foreignKey` is resolved from target related class                                                                    |
| `@HasOne(relatedModelGetter: () => typeof Model, foreignKey: string)`                                                         | sets `SourceModel.hasOne(RelatedModel, ...)` while `as` is key of annotated property and `foreignKey` is explicitly specified value                                                                            |
| `@HasOne(relatedModelGetter: () => typeof Model, options: AssociationOptionsHasOne)`                                          | sets `SourceModel.hasOne(RelatedModel, ...)` while `as` is key of annotated property and `options` are additional association options                                                                          |
| `@BelongsToMany(relatedModelGetter: () => typeof Model, through: (() => typeof Model))`                                       | sets `SourceModel.belongsToMany(RelatedModel, {through: ThroughModel, ...})` while `as` is key of annotated property and `foreignKey`/`otherKey` is resolved from through class                                |
| `@BelongsToMany(relatedModelGetter: () => typeof Model, through: (() => typeof Model), foreignKey: string)`                   | sets `SourceModel.belongsToMany(RelatedModel, {through: ThroughModel, ...})` while `as` is key of annotated property, `foreignKey` is explicitly specified value and `otherKey` is resolved from through class |
| `@BelongsToMany(relatedModelGetter: () => typeof Model, through: (() => typeof Model), foreignKey: string, otherKey: string)` | sets `SourceModel.belongsToMany(RelatedModel, {through: ThroughModel, ...})` while `as` is key of annotated property and `foreignKey`/`otherKey` are explicitly specified values                               |
| `@BelongsToMany(relatedModelGetter: () => typeof Model, through: string, foreignKey: string, otherKey: string)`               | sets `SourceModel.belongsToMany(RelatedModel, {through: throughString, ...})` while `as` is key of annotated property and `foreignKey`/`otherKey` are explicitly specified values                              |
| `@BelongsToMany(relatedModelGetter: () => typeof Model, options: AssociationOptionsBelongsToMany)`                            | sets `SourceModel.belongsToMany(RelatedModel, {through: throughString, ...})` while `as` is key of annotated property and `options` are additional association values, including `foreignKey` and `otherKey`.  |

Note that when using AssociationOptions, certain properties will be overwritten when the association is built, based on reflection metadata or explicit attribute parameters. For example, `as` will always be the annotated property's name, and `through` will be the explicitly stated value.

### Multiple relations of same models

_sequelize-typescript_ resolves the foreign keys by identifying the corresponding class references.
So if you define a model with multiple relations like

```typescript
@Table
class Book extends Model {
  @ForeignKey(() => Person)
  @Column
  authorId: number;

  @BelongsTo(() => Person)
  author: Person;

  @ForeignKey(() => Person)
  @Column
  proofreaderId: number;

  @BelongsTo(() => Person)
  proofreader: Person;
}

@Table
class Person extends Model {
  @HasMany(() => Book)
  writtenBooks: Book[];

  @HasMany(() => Book)
  proofedBooks: Book[];
}
```

_sequelize-typescript_ cannot know which foreign key to use for which relation. So you have to add the foreign keys
explicitly:

```typescript

  // in class "Books":
  @BelongsTo(() => Person, 'authorId')
  author: Person;

  @BelongsTo(() => Person, 'proofreaderId')
  proofreader: Person;

  // in class "Person":
  @HasMany(() => Book, 'authorId')
  writtenBooks: Book[];

  @HasMany(() => Book, 'proofreaderId')
  proofedBooks: Book[];
```

### Type safe usage of auto generated functions

With the creation of a relation, sequelize generates some method on the corresponding
models. So when you create a 1:n relation between `ModelA` and `ModelB`, an instance of `ModelA` will
have the functions `getModelBs`, `setModelBs`, `addModelB`, `removeModelB`, `hasModelB`. These functions still exist with _sequelize-typescript_.
But TypeScript wont recognize them and will complain if you try to access `getModelB`, `setModelB` or
`addModelB`. To make TypeScript happy, the `Model.prototype` of _sequelize-typescript_ has `$set`, `$get`, `$add`
functions.

```typescript
@Table
class ModelA extends Model {
  @HasMany(() => ModelB)
  bs: ModelB[];
}

@Table
class ModelB extends Model {
  @BelongsTo(() => ModelA)
  a: ModelA;
}
```

To use them, pass the property key of the respective relation as the first parameter:

```typescript
const modelA = new ModelA();

modelA
  .$set('bs', [
    /* instance */
  ])
  .then(/* ... */);
modelA.$add('b' /* instance */).then(/* ... */);
modelA.$get('bs').then(/* ... */);
modelA.$count('bs').then(/* ... */);
modelA.$has('bs').then(/* ... */);
modelA.$remove('bs' /* instance */).then(/* ... */);
modelA.$create('bs' /* value */).then(/* ... */);
```

## Indexes

### `@Index`

The `@Index` annotation can be used without passing any parameters.

```typescript
@Table
class Person extends Model {
  @Index // Define an index with default name
  @Column
  name: string;

  @Index // Define another index
  @Column
  birthday: Date;
}
```

To specify index and index field options, use
an object literal (see [indexes define option](https://sequelize.org/v5/manual/models-definition.html#indexes)):

```typescript
@Table
class Person extends Model {
  @Index('my-index') // Define a multi-field index on name and birthday
  @Column
  name: string;

  @Index('my-index') // Add birthday as the second field to my-index
  @Column
  birthday: Date;

  @Index({
    // index options
    name: 'job-index',
    parser: 'my-parser',
    type: 'UNIQUE',
    unique: true,
    where: { isEmployee: true },
    concurrently: true,
    using: 'BTREE',
    operator: 'text_pattern_ops',
    prefix: 'test-',
    // index field options
    length: 10,
    order: 'ASC',
    collate: 'NOCASE',
  })
  @Column
  jobTitle: string;

  @Column
  isEmployee: boolean;
}
```

#### Index API

| Decorator                                | Description                                                                                               |
| ---------------------------------------- | --------------------------------------------------------------------------------------------------------- |
| `@Index`                                 | adds new index on decorated field to `options.indexes`                                                    |
| `@Index(name: string)`                   | adds new index or adds the field to an existing index with specified name                                 |
| `@Table(options: IndexDecoratorOptions)` | sets both index and index field [options](https://sequelize.org/v5/manual/models-definition.html#indexes) |

### `createIndexDecorator()`

The `createIndexDecorator()` function can be used to create a decorator for an index with options specified with an object literal supplied as the argument. Fields are added to the index by decorating properties.

```typescript
const SomeIndex = createIndexDecorator();
const JobIndex = createIndexDecorator({
  // index options
  name: 'job-index',
  parser: 'my-parser',
  type: 'UNIQUE',
  unique: true,
  where: { isEmployee: true },
  concurrently: true,
  using: 'BTREE',
  operator: 'text_pattern_ops',
  prefix: 'test-',
});

@Table
class Person extends Model {
  @SomeIndex // Add name to SomeIndex
  @Column
  name: string;

  @SomeIndex // Add birthday to SomeIndex
  @Column
  birthday: Date;

  @JobIndex({
    // index field options
    length: 10,
    order: 'ASC',
    collate: 'NOCASE',
  })
  @Column
  jobTitle: string;

  @Column
  isEmployee: boolean;
}
```

## Repository mode

With `sequelize-typescript@1` comes a repository mode. See [docs](#repository-mode) for details.

The repository mode makes it possible to separate static operations like `find`, `create`, ... from model definitions.
It also empowers models so that they can be used with multiple sequelize instances.

### How to enable repository mode?

Enable repository mode by setting `repositoryMode` flag:

```typescript
const sequelize = new Sequelize({
  repositoryMode: true,
  ...,
});
```

### How to use repository mode?

Retrieve repository to create instances or perform search operations:

```typescript
const userRepository = sequelize.getRepository(User);

const luke = await userRepository.create({ name: 'Luke Skywalker' });
const luke = await userRepository.findOne({ where: { name: 'luke' } });
```

### How to use associations with repository mode?

For now one need to use the repositories within the include options in order to retrieve or create related data:

```typescript
const userRepository = sequelize.getRepository(User);
const addressRepository = sequelize.getRepository(Address);

userRepository.find({ include: [addressRepository] });
userRepository.create({ name: 'Bear' }, { include: [addressRepository] });
```

> ⚠️ This will change in the future: One will be able to refer the model classes instead of the repositories.

### Limitations of repository mode

Nested scopes and includes in general won't work when using `@Scope` annotation together with repository mode like:

```typescript
@Scopes(() => ({
  // includes
  withAddress: {
    include: [() => Address],
  },
  // nested scopes
  withAddressIncludingLatLng: {
    include: [() => Address.scope('withLatLng')],
  },
}))
@Table
class User extends Model {}
```

> ⚠️ This will change in the future: Simple includes will be implemented.

## Model validation

Validation options can be set through the `@Column` annotation, but if you prefer to use separate decorators for
validation instead, you can do so by simply adding the validate options _as_ decorators:
So that `validate.isEmail=true` becomes `@IsEmail`, `validate.equals='value'` becomes `@Equals('value')`
and so on. Please notice that a validator that expects a boolean is translated to an annotation without a parameter.

See sequelize [docs](https://sequelize.org/v5/manual/models-definition.html#validations)
for all validators.

### Exceptions

The following validators cannot simply be translated from sequelize validator to an annotation:

| Validator                       | Annotation                                                                                                                                                                  |
| ------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `validate.len=[number, number]` | `@Length({max?: number, min?: number})`                                                                                                                                     |
| `validate[customName: string]`  | For custom validators also use the `@Is(...)` annotation: Either `@Is('custom', (value) => { /* ... */})` or with named function `@Is(function custom(value) { /* ... */})` |

### Example

```typescript
const HEX_REGEX = /^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$/;

@Table
export class Shoe extends Model {
  @IsUUID(4)
  @PrimaryKey
  @Column
  id: string;

  @Equals('lala')
  @Column
  readonly key: string;

  @Contains('Special')
  @Column
  special: string;

  @Length({ min: 3, max: 15 })
  @Column
  brand: string;

  @IsUrl
  @Column
  brandUrl: string;

  @Is('HexColor', (value) => {
    if (!HEX_REGEX.test(value)) {
      throw new Error(`"${value}" is not a hex color value.`);
    }
  })
  @Column
  primaryColor: string;

  @Is(function hexColor(value: string): void {
    if (!HEX_REGEX.test(value)) {
      throw new Error(`"${value}" is not a hex color value.`);
    }
  })
  @Column
  secondaryColor: string;

  @Is(HEX_REGEX)
  @Column
  tertiaryColor: string;

  @IsDate
  @IsBefore('2017-02-27')
  @Column
  producedAt: Date;
}
```

## Scopes

Scopes can be defined with annotations as well. The scope options are identical to native
sequelize (See sequelize [docs](https://sequelize.org/master/manual/scopes.html) for more details)

### `@DefaultScope` and `@Scopes`

```typescript
@DefaultScope(() => ({
  attributes: ['id', 'primaryColor', 'secondaryColor', 'producedAt'],
}))
@Scopes(() => ({
  full: {
    include: [Manufacturer],
  },
  yellow: {
    where: { primaryColor: 'yellow' },
  },
}))
@Table
export class ShoeWithScopes extends Model {
  @Column
  readonly secretKey: string;

  @Column
  primaryColor: string;

  @Column
  secondaryColor: string;

  @Column
  producedAt: Date;

  @ForeignKey(() => Manufacturer)
  @Column
  manufacturerId: number;

  @BelongsTo(() => Manufacturer)
  manufacturer: Manufacturer;
}
```

## Hooks

Hooks can be attached to your models. All Model-level hooks are supported. See [the related unit tests](test/models/Hook.ts) for a summary.

Each hook must be a `static` method. Multiple hooks can be attached to a single method, and you can define multiple methods for a given hook.

The name of the method cannot be the same as the name of the hook (for example, a `@BeforeCreate` hook method cannot be named `beforeCreate`). That’s because Sequelize has pre-defined methods with those names.

```typescript
@Table
export class Person extends Model {
  @Column
  name: string;

  @BeforeUpdate
  @BeforeCreate
  static makeUpperCase(instance: Person) {
    // this will be called when an instance is created or updated
    instance.name = instance.name.toLocaleUpperCase();
  }

  @BeforeCreate
  static addUnicorn(instance: Person) {
    // this will also be called when an instance is created
    instance.name += ' 🦄';
  }
}
```

## PostgreSQL Alter Helper

When using PostgreSQL, `sync({ alter: true })` has several limitations that can cause errors:

1. **Column type changes require USING clauses** - PostgreSQL needs explicit conversion instructions
2. **ENUM type modifications are complex** - Adding/removing values requires special handling
3. **Duplicate constraints** - Multiple sync calls can create duplicate unique constraints
4. **Custom indexes** - Indexes with specific methods (GIN, GIST, etc.) need special care

The `PostgresAlterHelper` class provides utilities to handle these scenarios:

```typescript
import { Sequelize, PostgresAlterHelper } from 'sequelize-typescript';

const sequelize = new Sequelize({
  dialect: 'postgres',
  // ... connection options
});

const helper = new PostgresAlterHelper(sequelize);

// Change column type with USING clause
await helper.changeColumnType('Users', 'age', 'INTEGER', '"age"::integer');

// Add value to ENUM
await helper.addEnumValue('enum_Orders_status', 'cancelled');

// Replace entire ENUM
await helper.replaceEnum(
  'Orders',
  'status',
  'enum_Orders_status',
  ['pending', 'processing', 'completed', 'cancelled', 'refunded']
);

// Clean up duplicate constraints
await helper.cleanupDuplicateConstraints('Users', 'email');

// Create index with specific method
await helper.createIndexWithMethod('Articles', ['search_vector'], {
  name: 'idx_articles_search',
  using: 'GIN'
});
```

**Important**: The helper is meant for migrations, not for replacing proper migration files. Always use migration files in production.

See:
- [PostgreSQL ALTER Issues Documentation](docs/POSTGRESQL_ALTER_ISSUES.md) for detailed information
- [PostgreSQL Alter Helper Example](examples/postgres-alter-helper/) for usage examples

## Why `() => Model`?

`@ForeignKey(Model)` is much easier to read, so why is `@ForeignKey(() => Model)` so important? When it
comes to circular-dependencies (which are in general solved by node for you) `Model` can be `undefined`
when it gets passed to @ForeignKey. With the usage of a function, which returns the actual model, we prevent
this issue.

## Recommendations and limitations

### One Sequelize instance per model (without repository mode)

Unless you are using the [repository mode](#repository-mode), you won't be able to add one and the same model to multiple
Sequelize instances with differently configured connections. So that one model will only work for one connection.

### One model class per file

This is not only good practice regarding design, but also matters for the order
of execution. Since Typescript creates a `__metadata("design:type", SomeModel)` call due to `emitDecoratorMetadata`
compile option, in some cases `SomeModel` is probably not defined(not undefined!) and would throw a `ReferenceError`.
When putting `SomeModel` in a separate file, it would look like `__metadata("design:type", SomeModel_1.SomeModel)`,
which does not throw an error.

### Minification

If you need to minify your code, you need to set `tableName` and `modelName`
in the `DefineOptions` for `@Table` annotation. sequelize-typescript
uses the class name as default name for `tableName` and `modelName`.
When the code is minified the class name will no longer be the originally
defined one (So that `class User` will become `class b` for example).

## Contributing

To contribute you can:

- Open issues and participate in discussion of other issues.
- Fork the project to open up PR's.
- Update the [types of Sequelize](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/sequelize).
- Anything else constructively helpful.

In order to open a pull request please:

- Create a new branch.
- Run tests locally (`npm install && npm run build && npm run cover`) and ensure your commits don't break the tests.
- Document your work well with commit messages, a good PR description, comments in code when necessary, etc.

In order to update the types for sequelize please go to [the Definitely Typed repo](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/sequelize), it would also be a good
idea to open a PR into [sequelize](https://github.com/sequelize/sequelize) so that Sequelize can maintain its own types, but that
might be harder than getting updated types into microsoft's repo. The Typescript team is slowly trying to encourage
npm package maintainers to maintain their own typings, but Microsoft still has dedicated and good people maintaining the DT repo,
accepting PR's and keeping quality high.

**Keep in mind `sequelize-typescript` does not provide typings for `sequelize`** - these are seperate things.
A lot of the types in `sequelize-typescript` augment, refer to, or extend what sequelize already has.