sails/docs/concepts/ORM/Associations/OneWayAssociation.md

API-driven framework for building realtime apps, using MVC conventions (based on Express and Socket.io)

# One way association

**AKA "Belongs To"**

### Overview

A one way association is where a model is associated with another model.  You could query that model and [populate](https://sailsjs.com/documentation/reference/waterline-orm/queries/populate) to get the associated model.  You can't however query the associated model and populate to get the associating model.

### One Way Example

In this example, we are associating a `User` with a `Pet` but not a `Pet` with a `User`.

```javascript
// myApp/api/models/Pet.js
module.exports = {
  attributes: {
    name: {
      type: 'string'
    },
    color: {
      type: 'string'
    }
  }
}
```

```javascript
// myApp/api/models/User.js
module.exports = {
  attributes: {
    name: {
      type: 'string'
    },
    age: {
      type: 'number'
    },
    pony:{
      model: 'Pet'
    }
  }
}
```

Now that the association is setup, you can [populate](https://sailsjs.com/documentation/reference/waterline-orm/queries/populate) the pony association.

```javascript
var usersWithPonies = await User.find({ name:'Mike' }).populate('pony');
  // The users object would look something like:
  // [{
  //  name: 'Mike',
  //  age: 21,
  //  pony: {
  //    name: 'Pinkie Pie',
  //    color: 'pink',
  //    id: 5,
  //    createdAt: Tue Feb 11 2014 15:45:33 GMT-0600 (CST),
  //    updatedAt: Tue Feb 11 2014 15:45:33 GMT-0600 (CST)
  //  },
  //  createdAt: Tue Feb 11 2014 15:48:53 GMT-0600 (CST),
  //  updatedAt: Tue Feb 11 2014 15:48:53 GMT-0600 (CST),
  //  id: 1
  // }]
```

### Notes
> Because we have only formed an association on one of the models, a `Pet` has no restrictions on the number of `User` models it can belong to. If we wanted to, we could change this and associate the `Pet` with exactly one `User` and the `User` with exactly one `Pet`.


<docmeta name="displayName" value="One way association">