Enhanced Syntax and Behavior for `hasOneThrough` and `hasManyThrough` Relationships in Laravel's Eloquent ORM

[rajubeparybd]

Synopsis:

The hasOneThrough and hasManyThrough relationships in Laravel's Eloquent ORM allow you to define indirect associations between models by going through intermediate models. These relationships are useful when you have a chain of relationships and want to access related models through that chain.

Proposed Syntax:

Yaml would use the following syntax:

hasOneThrough:
  - model: TargetModel
  - through: IntermediateModel
  
hasManyThrough:
  - model: TargetModel
  - through: IntermediateModel

To define a hasOneThrough relationship, you would use the following syntax:

public function targetModel()
{
    return $this->hasOneThrough(TargetModel::class, IntermediateModel::class);
}

To define a hasManyThrough relationship, you would use the following syntax:

public function targetModels()
{
    return $this->hasManyThrough(TargetModel::class, IntermediateModel::class);
}

Expected Behavior:

When you define a hasOneThrough or hasManyThrough relationship, Laravel will automatically generate the necessary SQL queries to retrieve the related models through the intermediate model.

For example, if you have the following models: User, Role, and Permission, and you want to define a hasOneThrough relationship between User and Permission through the Role model, you would use the following code:

class User extends Model
{
    public function permission()
    {
        return $this->hasOneThrough(Permission::class, Role::class);
    }
}

Now, you can access the Permission model associated with a User instance using the permission dynamic property:

$user = User::find(1);
$permission = $user->permission; // Retrieves the permission associated with the user

Similarly, if you want to define a hasManyThrough relationship, you would use the same syntax, but the relationship method would return a collection of related models:

class User extends Model
{
    public function permissions()
    {
        return $this->hasManyThrough(Permission::class, Role::class);
    }
}

Now, you can access the collection of Permission models associated with a User instance using the permissions dynamic property:

$user = User::find(1);
$permissions = $user->permissions; // Retrieves the collection of permissions associated with the user

[jasonmccreary]

I am glad to support the has*Through relationships. I don't like the proposed syntax. I'd like something a little more streamlined, such as:

hasOneThrough: TargetModel:IntermediateModel, AnotherModel:AnotherIntermediateModel

This way it is like the other relationships.

[rajubeparybd]

There should be a way to pass the local and foreign keys for those tables. The foreign key should be optional. Follow Laravel Docs

The syntax when the Foreign key is set:

hasOneThrough: TargetMode.foreignKey:IntermediateModel.foreignKey, AnotherModel.foreignKey:AnotherIntermediateModel.foreignKey

The syntax when the Foreign key is not set:

hasOneThrough: TargetModel:IntermediateModel, AnotherModel:AnotherIntermediateModel

[impeto]

If we follow the Laravel docs, we can have something like this:

Project:
  relationships:
    hasManyThrough: Deployment, Environment, project_id, environment_id, id, id

With the foreign and local keys optional.

[jasonmccreary]

Again, I am open to this. But it needs to be more streamlined.