Types

A type defines a data structure that a plugin can infer to provide queries and mutations. Types can also be used while defining queries and mutations. A type defines a set of fields that may be scalar types or other types. For example, the following type defines a Todo type with three fields: id, title, and completed.

@postgres
module TodoPersistence {
  type Todo {
    id: Int
    title: String
    completed: Boolean
  }
}

The plugin (in this case, the Postgres plugin) will interpret the type definition as a database entity and create queries such as todos and todo to retrieve the entities from the database, as well as mutations such as createTodo and updateTodo to create and update the entities in the database.

Exograph supports optional semi-colons at the end of each line. Therefore, the above definition is equivalent to the following:

@postgres
module TodoPersistence {
  type Todo {
    id: Int;
    title: String;
    completed: Boolean;
  }
}

Each type may carry annotations, and as you may have guessed by now, the plugin is responsible for interpreting those. For example, the Postgres plugin will interpret the @table annotation as the table's name in the database to override the one inferred from the type name.

Fragments

Fragments allow you to specify a group of fields that are used together. For example, you may have types that have a name field and an email field. You may want to create a fragment that contains both of these fields.

@postgres
module UserPersistence {
  fragment UserInfoFragment {
    @pk id: Int = autoIncrement()
    name: String
    email: String
  }

  type Employee {
    ...UserInfoFragment
    manager: Manager
  }

  type Manager {
    ...UserInfoFragment
    employees: Set<Employee>
  }
}

Fragments are often used to reflect the structure of the database and can be spliced into other types where you may specify access control rules. See exo schema import for an automatic way to create fragments from an existing database.

Fragments​

Fragments