Custom Types

In addition to primitive types, you can define custom types in Camille. The following commands will generate type definition files in config/camille/types.

# to generate a type named Product
rails g camille:type product
# to generate a type named Nested::Product
rails g camille:type nested/product

Each custom type is considered a type alias in TypeScript, and alias_of defines what this type is aliasing:

using Camille::Syntax

class Camille::Types::Product < Camille::Type
  include Camille::Types

  alias_of(
    id: Number,
    name: String
  )
end

export type Product = {
  id: number,
  name: string
}

In this case, the Product type is an alias of an object type having fields id as Number and name as String.

Once defined, Product can be used anywhere a type is expected in a schema or another type, see Type Syntax.

Checking a value

You can perform a type check on a value using check, which can be handy in testing:

# `check` will return either a Camille::Checked or a Camille::TypeError
result = Camille::Types::Product.check(hash)
if result.checked?
  # the hash is accepted by Camille::Types::Product type
else
  p result
end