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Attributes

Overview

Model attributes are basic pieces of information about a model. For example, a model called Person might have attributes named firstName, lastName, phoneNumber, age, birthDate and emailAddress.

Defining attributes

A model's attributes setting allows you to provide a set of attributes, each defined as a dictionary (a plain JavaScript object):

// api/models/User.js
{
  attributes: {
    emailAddress: { type: 'string', required: true, },
    karma: { type: 'number', },
    isSubscribedToNewsletter: { type: 'boolean', defaultsTo: true, },
  },
}

Within each attribute, there are one or more keys—or options—which are used to provide additional direction to Sails and Waterline. These attribute keys tell the model how to go about ensuring type safety, enforcing high-level validation rules, and (if you have automigrations enabled) how it should go about setting up tables or collections in your database.

Default attributes

You can also define default attributes that will appear in all of your models, by defining attributes as a default model setting (e.g. in config/models.js). For example, new Sails apps come with three default attributes out of the box: id, createdAt, and updatedAt.

These attributes will be available in all models unless they are overridden or disabled. To override a default attribute, define an attribute with the same name in the model definition. To disable a default attribute, define it as false. For instance, to disable the default updatedAt attribute for a particular model:

// api/models/ProductCategory.js
module.exports = {
  attributes: {
    updatedAt: false,
    label: { type: 'string', required: true },
  }
}

Type safety

Type

Except for associations, every attribute must declare a type.

This is the type of data that will be stored for this attribute and used for logical type safety checks of queries and results. Here is a list of the data types supported by Sails and Waterline:

• string
• number
• boolean
• json
• ref

Required

If an attribute is required: true, then a value must always be specified for it when calling .create(). This prevents the attribute value from being created as or updated to null or empty string ("").

Default values

In addition to the five data types, there are a couple of other basic guarantees that you can define for an attribute; one of these is the ability to assign it a default value.

The default value (defaultsTo) of an attribute only applies on .create(), and only when the key is omitted entirely.

attributes: {
  phoneNumber: {
    type: 'string',
    defaultsTo: '111-222-3333'
  }
}

Allow Null

The string, number, and boolean data types do not accept null as a value when creating or updating records. In order to allow a null value to be set, you can toggle the allowNull flag on the attribute. Note that the allowNull flag is only valid on the data types listed above. It is not valid on attributes with types json or ref, any associations, or any primary key attributes.

attributes: {
  phoneNumber: {
    type: 'string',
    allowNull: true
  }
}

Validations

In addition to basic type safety checks, Sails offers several different high-level validation rules. For example, the isIn rule verifies that any new value stored for this attribute must exactly match one of a few different hard-coded constants:

unsubscribeReason: {
  type: 'string',
  isIn: ['boring', 'too many emails', 'recipes too difficult', 'other'],
  required: true
}

For a complete list of high-level validation rules, see Validations.

columnName

Inside an attribute definition, you can specify a columnName to force Sails/Waterline to store data for that attribute in a specific column in the configured datastore (i.e. database). Be aware that this is not necessarily SQL-specific—it will also work for MongoDB fields, etc.

While the columnName property is primarily designed for working with existing/legacy databases, it can also be useful in situations where your database is being shared by other applications, or those in which you don't have access permissions to change the schema.

To store/fetch your model's numberOfWheels attribute into/from the number_of_round_rotating_things column:

// An attribute in one of your models:
  // ...
  numberOfWheels: {
    type: 'number',
    columnName: 'number_of_round_rotating_things'
  }
  // ...

Now for a more comprehensive example.

Let's say you have a User model in your Sails app that looks like this:

// api/models/User.js
module.exports = {
  datastore: 'shinyNewMySQLDatabase',
  attributes: {
    name: {
      type: 'string'
    },
    password: {
      type: 'string'
    },
    email: {
      type: 'string',
      unique: true
    }
  }
};

Everything works great, but instead of using an existing MySQL database sitting on a server somewhere that happens to house your app's intended users...

// config/datastores.js
module.exports = {
  // ...

  // Existing users are in here!
  rustyOldMySQLDatabase: {
    adapter: 'sails-mysql',
    url: 'mysql://ofh:Gh19R!?@db.eleven.sameness.foo/jonas'
  },
  // ...
};

... let's say there's a table called our_users in the old MySQL database that looks like this:

the_primary_key	email_address	full_name	seriously_hashed_password
7	mike@sameness.foo	Mike McNeil	ranchdressing
14	nick@sameness.foo	Nick Crumrine	thousandisland

In order to use this from Sails, you'd change your User model to look like this:

// api/models/User.js
module.exports = {
  datastore: 'rustyOldMySQLDatabase',
  tableName: 'our_users',
  attributes: {
    id: {
      type: 'number',
      unique: true,
      columnName: 'the_primary_key'
    },
    name: {
      type: 'string',
      columnName: 'full_name'
    },
    password: {
      type: 'string',
      columnName: 'seriously_hashed_password'
    },
    email: {
      type: 'string',
      unique: true,
      columnName: 'email_address'
    }
  }
};

You might have noticed that we also used the tableName property in this example. This allows us to control the name of the table that will be used to house our data.

Encryption at rest

encrypt

Setting encrypt allows you to decide whether this attribute should be automatically encrypted. If set to true, when a record is retrieved, it will still contain the encrypted value for this attribute unless .decrypt() is used.

attributes: {
  ssn: {
    type: 'string',
    encrypt: true
  }
}

If you're using encrypt: true for an attribute, you won't be able to look up records by the unencrypted value.

Automigrations

These settings are used to indicate how Sails should create the physical-level (e.g. PostgreSQL, MySQL or MongoDB) database field for an attribute when an app is lifted.

When a model’s migrate property is set to safe, these settings will be ignored and the database columns will remain unchanged.

columnType

Indicates the type of physical-level column data type to use for an attribute when Sails creates the database table. This allows you to specify types that are tied directly to how your underlying database will create them. For example, you may have an attribute that sets its type property to number and to store that in the database you want to use the column type float. Your attribute definition would look like:

attributes: {
  placeInLine: {
    type: 'number',
    columnType: 'float'
  }
}

• Column types are entirely database-dependent. Be sure that the columnType you select corresponds to a data type that is valid for your database! If you don’t specify a columnType, the adapter will choose one for you based on the attribute’s type.
• The columnType value is used verbatim in the statement that creates the database column, so you can use it to specify additional options, e.g. varchar(255) CHARACTER SET utf8mb4.
• If you intend to store binary data in a Sails model, you’ll want to set the type of the attribute to ref, and then use the appropriate columnType for your chosen database (e.g. mediumblob for MySQL or bytea for PostgreSQL). Keep in mind that whatever you attempt to store will have to fit in memory before being transferred to the database, as there is currently no mechanism in Sails for streaming binary data to a datastore adapter. As an alternative to storing blobs in a database, you might consider streaming them to disk or to a remote filesystem like S3, using the .upload() method.
• Keep in mind that custom column options like CHARACTER SET utf8mb4 in MySQL can affect a column’s storage size. This is especially relevant when used in conjunction with the unique property, where you may have to specify a smaller column size to avoid errors. See the unique property docs below for more info.

autoIncrement

Sets up the attribute as an auto-increment key. When a new record is added to the model, if a value for this attribute is not specified, it will be generated by incrementing the most recent record's value by one. Note: attributes that specify autoIncrement should always be of type: 'number'. Also bear in mind that the level of support varies across different datastores. For instance, MySQL will not allow more than one auto-incrementing column per table.

attributes: {
  placeInLine: {
    type: 'number',
    autoIncrement: true
  }
}

unique

Ensures no two records will be allowed with the same value for the target attribute. This is an adapter-level constraint, so in most cases this will result in a unique index on the attribute being created in the underlying datastore.

attributes: {
  username: {
    type: 'string',
    unique: true
  }
}

Depending on your database, when using unique: true, you may also need set required: true.

When using unique: true on an attribute with the utf8mb4 character set in a MySQL database, you will need to set the column size manually via the columnType property to avoid a possible 'index too long' error. For example: columnType: varchar(100) CHARACTER SET utf8mb4.