has_one

Has many represents the second counter part of belongs to relation. It assumes the current model is referenced by an object (or no objects) of another model.

Usually, it's used when another model optionally extend the current model by composition. A common example is the usage of User and UserInfo. UserInfo is setup after registration and filling of form from the user. An User can then exists without UserInfo – this handle all the connection lifecycle – while UserInfo will handle all the optional informations about the user.

class User
  include Clear::Model

  primary_key

  has_one user_info : UserInfo
end

class UserInfo
  include Clear::Model

  primary_key

  belongs_to user : User
end