Return calculated custom attribute from Laravel Pivot - php

Question

I'm building a service API and would like to return a calculated date called 'expire_at' in my JSON response for 'subscriptions' relation below. The date will be calculated based on knowing 'activated_at', 'interval' and 'interval_type'. This can of course be calculated on the front-end, but I would like to provide this conveniently in my API response. I can't figure out where to put the logic though.
I could put it in the Plan model using the $appends property, but that would only work when requesting plans from a Customer. Putting it in the CustomerController would require looping through each subscription for each customer.
Where should I put the logic of calculating this date for each subscription in the customer result? Are above places my only two options?
Customer JSON result: (with 'expire_at' added)
{
id: 4327,
name: "Test Company",
created_at: "2014-05-29 21:12:37",
updated_at: "2014-05-29 21:12:37",
subscriptions: [
{
id: 93754,
name: "Test standard plan",
description: "An example subscription plan",
...
created_at: "2014-05-29 21:12:37",
updated_at: "2014-05-29 21:12:37",
activated_at: "2014-05-29 00:00:00",
active: true,
renewal_active: false,
// expire_at: "2014-06-28 00:00:00",
interval: 1,
interval_type_name: "Monthly"
}
]
}
Plan model:
class Plan extends Eloquent {
protected $guarded = array('id');
protected $hidden = array('pivot');
public function customers()
{
return $this->belongsToMany('Customer');
}
}
Customer model:
class Customer extends Eloquent {
protected $guarded = array('id');
public function users()
{
return $this->hasMany('User');
}
public function subscriptions()
{
return $this->belongsToMany('Plan')->withPivot('activated_at as activated_at', 'active as active', 'renewal_active as renewal_active');
}
}
Customer Controller
public function show($id)
{
$customer = Customer::with('subscriptions')->find($id);
return Response::json($customer);
}

Answer 1

You could store the logic to produce the expire_at attribute in the pivot table.
To achieve this you need to create the pivot model with the logic and than tell Laravel how to use it.
Pivot model:
class Subscription extends Eloquent
{
protected $table = 'customer_plan'; // point this to your pivot table
protected $appends = array('expires_at');
public function getExpiresAtAttribute()
{
return 'tomorrow';
}
public function customer()
{
return $this->belongsTo('Customer');
}
public function plan()
{
return $this->belongsTo('Plan');
}
}
Now we tell Laravel that Customer and Plan should use the Subscription model.
Customer model:
class Customer extends Eloquent
{
public function subscriptions()
{
return $this->hasMany('Subscription');
}
}
Plan model:
class Plan extends Eloquent
{
public function subscriptions()
{
return $this->hasMany('Subscription');
}
}
The query to fetch the data changes slightly:
$customer = Customer::with('subscriptions.plan')->find($id);
return Response::json($customer);