Can we use an observer on the attach method in Laravel? - laravel

I would like to observe a pivot table in which, rows are created with an attach method in a specific model, is there a way to Observe that pivot table through the attach method that is responsible for creating rows?

after struggling some time, I came to answer my question,
so in order to observe a table whose rows are created by the attach method, we will need to do 3 things
1- we will need to create a model that extends
$Illuminate\Database\Eloquent\Relations\Pivot
2- Connect the model to the database table with this line:
protected $table = 'data_base_table_name';
3- use the method 'using' at the end of the BelongsToMany relationship in each model that is related to the pivot table
Example:
let's say we have a model called Student and another one called Group, we have also a pivot table called group_students that is filled with the attach method since we have a student BelongsToMany groups and Group BelongsToMany Students,
we will need to create a model named GroupStudent that extends
Illuminate\Database\Eloquent\Relations\Pivot
and link it to the group_students by adding the following line in the GroupStudent Class:
protected $table = 'group_student'
After that, we will need to add the using method The BelongsToMany relations in the Student Model and the Group Model like the following:
public function students()
{
return $this->BelongsToMany(Student::class)->using(GroupStudent::class);
}
and
public function groups()
{
return $this->belongsToMany(Group::class)->using(GroupStudent::class);
}
And here we go, now whenever I create a row in the group_students table through the attach method, this will be observed and the method created will be executed.

Related

hasOneThrough relationship Laravel

A contract has a representative (which is a user).
Currently I get this relationship with an belongsTo directly like this in my Contract model:
class Contract extends Model
{
public function representative()
{
return $this->belongsTo(User::class);
}
I would like to be able to retrieve this relationship through the organization_user table and retrieve the "position" attribute.
I think I should use the hasOneThrough relationship but I can't get what I'm looking for.
class Contract extends Model
{
public function representative()
{
return $this->hasOneThrough(User::class, OrganizationUser::class);
}
Not sure if you're in a position to change your DB structure, but it seems to me that your table contracts and organization_user are duplicating each other, storing the same data.
Would it make sense to leave only one table organization_user as a pivot table with the position?
Then you wouldn't need to make the big loop over few relationship to get the needed data.

Laravel: Retrieve records from a table with an associated table via another table

here is my problem.
I have 3 tables:
bookings (id, spot_id,...)
a booking have one spot and a spot have multiple bookings
spots (id, place_id,...)
a spot have one place and a place have multiple spots
places(id, ...)
And what i want is from the BookingController get
a list of bookings with their associated places
somethings like that:
Booking::where("ok",1)->with("place")->get();
i already have the "hasMany" and "belongsTo" relations in all three models. And i already tried "hasOneThrough" in booking model but to no avail.
how can i do that thanks.
If you always want to have the places included in the booking model you can add those as an attribute:
namespace App\Models;
class Booking{
public $appends = ['places'];
public function getPlacesAttribute()
{
return $this->hasMany(Place::class);
}
}
Now you can acces places directly from the booking class like $booking->places

Nested eloquent relationship

I just started my first laravel project today and stumbled upon this confusing situation,
I intended to use eloquent relationship instead of manually joining tables on query. So here it goes...
I have 3 tables which are users , tbl_instruments_taught , tbl_instruments
users table does not hold any of the table's ID,
tbl_instruments_taught - holds the id of user and intruments
Note: user can teach multiple instruments
Now, I implemented a hasOne on my other result set but I dont think hasOne works on this one. I read about belongsToMany but as I try implement it, it seems like every minute, it gets confusing.
Any idea?
I think you are looking for pivot table and relation many to many.
You have users table, instruments table (user has many instruments and one instrument could belong to many users) and user_instruments pivot table. Here db model:
And then add belongsToMany relationship in User and Instrument model (with specified pivot table). Like so:
//IN USER MODEL
public function instruments()
{
return $this->belongsToMany('App\Models\Instruments', 'users_instruments', 'user_id', 'instrument_id');
}
//IN INSTRUMENT MODEL
public function users()
{
return $this->belongsToMany('App\Models\Users', 'users_instruments', 'insrument_id', 'user_id');
}
Now you can reach instruments/users data through laravel relations/eager loading.

Laravel 5.5 retrieving null by nested relation

I have 3 databases:
Routes:
id
name
Rates:
Id
Route_id
Car_id
Cars:
id
name
My model for routes
public function rates()
{
return $this->hasMany('App\Rate', 'route_id');
}
My model for rates
public function car() {
return $this->belongsTo('App\Car','car_id');
}
Now I need to access the car relation, but when I do
return $this->route->with('from','to','rates.car')->paginate(74);
I get null for the car relation
{"id":1,"from_id":1,"to_id":2,"distance":400,"created_at":null,"updated_at":null,"from":{"id":1,"name":"\u0410\u043a\u043a\u043e","created_at":null,"updated_at":null,"lat":32.93310000000000314912540488876402378082275390625,"long":35.0827000000000026602720026858150959014892578125},"to":{"id":2,"name":"\u0410\u0440\u0430\u0434","created_at":null,"updated_at":null,"lat":31.261399999999998300381776061840355396270751953125,"long":35.21490000000000009094947017729282379150390625},"rates":[{"id":1,"route_id":1,"car_id":1,"rate":1123,"night_rate":1391,"car":null},{"id":5551,"route_id":1,"car_id":2,"rate":1123,"night_rate":1391,"car":null},{"id":11101,"route_id":1,"car_id":3,"rate":1123,"night_rate":1391,"car":null},{"id":16651,"route_id":1,"car_id":4,"rate":1123,"night_rate":1391,"car":null},{"id":22201,"route_id":1,"car_id":5,"rate":1123,"night_rate":1391,"car":null},{"id":27751,"route_id":1,"car_id":6,"rate":1123,"night_rate":1391,"car":null},{"id":33301,"route_id":1,"car_id":7,"rate":1123,"night_rate":1391,"car":null},{"id":38851,"route_id":1,"car_id":8,"rate":1123,"night_rate":1391,"car":null}]},
From my understanding you are trying to access a Car model through a Route model.
A couple of things I noticed that should help you find a solution.
First off I think the inverse relation you are supposed to use the belongToMany() function instead.
public function car() {
return $this->belongsToMany('App\Car','Rates'); // Perhaps call the table something like routes_cars to more clearly define it's a pivot table
}
Next I see you are trying to use model functions within the context of $this(). I assume you are doing this in your model? That logic should be in a controller, that might cause some undesired results but I'm not entirely sure. Also it looks like your parameters are incorrect when using with(). You use the function name that you defined in belongsToMany()
App/Route::with('car')->paginate(74);
With the correct relationships setup you rarely need to worry about the pivot table. If you are going to add extra information in the pivot table there are laravel functions to help you do that in the documentation.

Laravel / Eloquent - custom relation method

I have a class Report which has a belongsToMany relation to Metric. Report also additionally has a belongsTo relation to Metric.
Normally, the model returned by the belongsTo relation is the same as one of the models in the belongsToMany relation. When this is true I'd like it to be the case that each of the two relations actually looks at the same object instance (this also saves an extra trip to the db).
So, in basic terms - is there a way to get one relation to check another first, to see if a model has already been loaded, and if so, point to that object rather than creating a new one.
I tried putting some code in the belongsTo relation method for Metric but I can't get round the fact it needs to return an instance of belongsTo, which needs various things passed as constructor arguments (ie. a query object), which aren't relevant in that case that the model has already been loaded in the belongsToMany relation.
I thought of ditching the belongsTo relation and adding data horizontally in the pivot table for the belongsToMany relation, but it isn't a many-to-many relation required so that seems a bit wrong.
Thanks!
Geoff
The idea here is to write a function which would check if a relationship is loaded and return that relationship, otherwise it will return the belongsToMany. This would go in your Report class. This is also for Laravel 5. If you have 4, just remove the namespaces from the model names.
public function metric()
{
return $this->belongsTo('App\Metric');
}
public function metrics()
{
return $this->belongsToMany('App\Metric');
}
public function getMetric()
{
if(array_key_exists('metric', $this->getRelations())) {
return $this->metric;
}
return $this->metrics()->first();
}
If you do decide to just go with a belongsToMany only, I'd suggest putting a unique key on your pivot table for both ID's to keep from getting any duplicates in the pivot table.

Resources