# Has One

pub struct Hero {
    pub location: HasOne<Uuid, location, Location>

HasOne fields are an abstraction over Diesel model fields (i.e database forign keys). The HasOne type takes the type of the underlying field (in this case a Uuid), the referenced models schema and the referenced model itself.

At compile time, this is removed and the Diesel model Hero will be given a simple Uuid location field. However, our GraphQL schema will show location to have a type of Location and querying for a Heros location will allow access to the full type!

HasOne takes the form of HasOne<Primary Key Type, Type Schema, Type Diesel Model>.