# hasMany

## Defining

A `hasMany` relationship is a `one-to-many` relationship. For instance, a `User` may have multiple `Posts`.

```javascript
// User.cfc
component extends="quick.models.BaseEntity" {

    function posts() {
       return hasMany( "Post" );
    }

}
```

The first value passed to `hasMany` is a WireBox mapping to the related entity.

Quick determines the foreign key of the relationship based on the entity name and key values. In this case, the `Post` entity is assumed to have a `userId` foreign key. You can override this by passing a foreign key in as the second argument:

```javascript
return hasMany("Post", "FK_userID");
```

If your parent entity does not use `id` as its primary key, or you wish to join the child entity to a different column, you may pass a third argument to the `belongsTo` method specifying your parent table's custom key.

```javascript
return hasMany("Post", "FK_userID", "relatedPostId");
```

The inverse of `hasMany` is also [`belongsTo`](https://quick.ortusbooks.com/2.0.0/relationships/relationship-types/belongsto).

```javascript
// Post.cfc
component extends="quick.models.BaseEntity" {

    function user() {
        return belongsTo( "User" );
    }

}
```

## Inserting & Updating

There are two ways to add an entity to a `hasMany` relationship. Both mirror the [insert API](https://quick.ortusbooks.com/2.0.0/getting-started/creating-new-entities) for entities.

### save

You can call the `save` method on the relationship passing in an entity to relate.

```javascript
var post = getInstance( "Post" ).fill( {
    "title" = "My Post",
    "body" = "Hello, world!"
} );

var user = getInstance( "User" ).findOrFail( 1 );

user.posts().save( post );
```

This will add the `User` entity's id as a foreign key in the `Post` and save the `Post` to the database.

> **Note:** the `save` method is called on the `posts` relationship, not the `getPosts` collection.

### create

Use the `create` method to create and save a related entity directly through the relationship.

```javascript
var user = getInstance( "User" ).findOrFail( 1 );

user.posts().create( {
    "title" = "My Post",
    "body" = "Hello, world!"
} );
```

This example will have the same effect as the previous example.

## Removing

Removing a `hasMany` relationship is handled in two ways: either by using the `dissociate` method on the [`belongsTo`](https://quick.ortusbooks.com/2.0.0/relationships/relationship-types/belongsto) side of the relationship or by deleting the [`belongsTo`](https://quick.ortusbooks.com/2.0.0/relationships/relationship-types/belongsto) side of the relationship.