Has Many Through

The "has-many-through" relationship provides a convenient way to access distant relations via an intermediate relation. For example, let's assume we are building a deployment platform. A Project model might access many Deployment models through an intermediate Environment model. Using this example, you could easily gather all deployments for a given project. Let's look at the tables required to define this relationship:

projects
    id - integer
    name - string

environments
    id - integer
    project_id - integer
    name - string

deployments
    id - integer
    environment_id - integer
    commit_hash - string

Now that we have examined the table structure for the relationship, let's define the relationship on the Project model:

class Project extends Model {
  /**
   * Get all of the deployments for the project.
   */
  @HasManyThroughColumn({
    related: forwardRef(() => Deployment),
    through: forwardRef(() => Environment)
  })
  public deployments: FedacoRelationType<Deployment[]>;
}

The related argument passed to the HasManyThroughColumn annotation is the name of the final model we wish to access, while the through argument is the name of the intermediate model.

Key Conventions

Typical Fedaco foreign key conventions will be used when performing the relationship's queries. If you would like to customize the keys of the relationship, you may pass them as the firstKey and secondKey config to the hasManyThrough method. The firstKey argument is the name of the foreign key on the intermediate model. The secondKey argument is the name of the foreign key on the final model. The localKey argument is the local key, while the secondLocalKey argument is the local key of the intermediate model:

class Project extends Model {
  @HasManyThroughColumn({
    related: Deployment,
    through: Environment,
    firstKey: 'project_id',
    secondKey: 'environment_id',
    localKey: 'id',
    secondLocalKey: 'id'
  })
  public deployments: FedacoRelationType<Deployment[]>;
}