One-to-One

Overview

A one-to-one association states that a model may only be associated with one other model. In order for the model to know which other model it is associated with, a foreign key must be included in the record.

One-to-One Example

In this example, we are associating a Pet with a User. The User may only have one Pet and viceversa, a Pet can only have one User. However, in order to query this association from both sides, you will have to create/update both models.

myApp/api/models/pet.js

module.exports = {

    attributes: {
        name:'STRING',
        color:'STRING',
        owner:{
            model:'user'
        }
    }

}

myApp/api/models/user.js

module.exports = {

    attributes: {
        name:'STRING',
        age:'INTEGER',
        pony:{
            model: 'pet'
        }
    }

}

Using sails console

sails> User.create({ name: 'Mike', age: 21}).exec(console.log);
null { name: 'Mike',
  age: 21,
  createdAt: Thu Feb 20 2014 17:12:18 GMT-0600 (CST),
  updatedAt: Thu Feb 20 2014 17:12:18 GMT-0600 (CST),
  id: 1 }

sails> Pet.create({ name: 'Pinkie Pie', color: 'pink', owner: 1}).exec(console.log)
null { name: 'Pinkie Pie',
    color: 'pink',
    owner: 1,
    createdAt: Thu Feb 20 2014 17:26:16 GMT-0600 (CST),
    updatedAt: Thu Feb 20 2014 17:26:16 GMT-0600 (CST),
    id: 2 }

sails> Pet.find().populate('owner').exec(console.log)
null [ { name: 'Pinkie Pie',
    color: 'pink',
    owner: 
     { name: 'Mike',
       age: 21,
       id: 1,
       createdAt: Thu Feb 20 2014 17:12:18 GMT-0600 (CST),
       updatedAt: Thu Feb 20 2014 17:12:18 GMT-0600 (CST) },
    createdAt: Thu Feb 20 2014 17:26:16 GMT-0600 (CST),
    updatedAt: Thu Feb 20 2014 17:26:16 GMT-0600 (CST),
    id: 2 } ]

sails> User.find().populate('pony').exec(console.log)
null [ { name: 'Mike',
    age: 21,
    createdAt: Thu Feb 20 2014 18:11:15 GMT-0600 (CST),
    updatedAt: Thu Feb 20 2014 18:11:15 GMT-0600 (CST),
    id: 2,
    pony: undefined } ]

sails> User.update({name:'Mike'},{pony:2}).exec(console.log)
null [ { name: 'Mike',
    age: 21,
    createdAt: Thu Feb 20 2014 17:12:18 GMT-0600 (CST),
    updatedAt: Thu Feb 20 2014 17:30:58 GMT-0600 (CST),
    id: 1,
    pony: 2 } ]

sails> User.findOne(1).populate('pony').exec(console.log)
null { name: 'Mike',
  age: 21,
  createdAt: Thu Feb 20 2014 17:12:18 GMT-0600 (CST),
  updatedAt: Thu Feb 20 2014 17:30:58 GMT-0600 (CST),
  id: 1,
  pony: 
   { name: 'Pinkie Pie',
     color: 'pink',
     id: 2,
     createdAt: Thu Feb 20 2014 17:26:16 GMT-0600 (CST),
     updatedAt: Thu Feb 20 2014 17:26:16 GMT-0600 (CST),
     owner: 1 } }

Notes

For a more detailed description of this type of association, see the Waterline Docs