Attributes

Summary

In this lesson, we explore the core concept of attributes in Waterline models. Since attributes define the structure of a model, they are the most crucial part of model definitions in Sails. Attributes represent information about a model, similar to how a person might have properties like name and age. Each attribute is defined within the attributes object of a model and is assigned a type. Waterline uses this type to determine how the attribute should be stored in the underlying database. Additional properties like required and validation rules can be specified to enforce constraints. With auto-migration enabled, lifting Sails will create corresponding columns in the database.

Transcript

Now we've seen how to create a Waterline model using the sails generate model command. Let's look at the model definition itself, especially attributes, because this is where you'll spend about 80% of the time when working with Waterline models.

So, what are attributes really? Attributes define the structure of a model. For example, if we have a model representing a person, this person would have attributes like name and age. Similarly, in the User model we've seen in previous lessons, it has attributes such as name and age. Essentially, attributes represent the properties of a model.

Let's look at the Product model as an example. Inside the Product model, we have an attributes object where we define the properties of the model. Each property takes an object that specifies additional details for Waterline and Sails. These details may include:

• The type, which is the only required property. Waterline uses this to determine the column type in the database.

• Constraints like required to enforce mandatory fields.

• Validation rules or type safety checks.

For instance, in our Product model, we might define:

attributes: {
  name: {
    type: 'string'
  },
  description: {
    type: 'string'
  }
}

With auto-migration enabled, lifting Sails will automatically create the corresponding columns in the database. If we check our database using Beekeeper, we should see the Product model with name and description columns.

You might notice additional attributes appearing in the database that we haven’t explicitly defined. That’s because Waterline and Sails automatically add certain attributes to models. These attributes and their significance will be covered in the next lesson.