I have an understanding issue with Laravel Eloquent Models and relations.
I have a user table user. These users can add car license plates, which I save in user_plates. I have a database which contains car models and types. The table name is cars. I have the models App\User, App\UserPlates and App\Car.
The user_plates table has the fields id,plate,user_id,car_id.
I save the plate, the associated user (in user_id) and the selected car (car_id (id from table cars))
I added plates() with belongTo function to my User Model which already successfully returns all plates associated with that user. But now I want to get the associated car (car_id inside user_plates). How do I achieve this using Eloquent? The car table does not have any connection to the user table, only user_plates has a car_id and a user_id.
I need to achieve this:
User -> Plates (can be multiple) -> Plate -> Car. I know how to achieve this using simple MySQL Joins but I want to do it right with Eloquent. Thanks for any help!
Laravel: 6.4.0
So, if your database is set up as...
users user_plates cars
----- ----------- ----
id id id
etc. plate etc.
user_id
car_id
Your models are set up as...
// in model: User
public function user_plates()
return $this->hasMany('UserPlate'); // fill out fully qualified name as appropriate…
// in model: UserPlate
public function user()
return $this->belongsTo('User');
public function car()
return $this->belongsTo('Car');
// in model: Car
public function user_plates()
return $this->hasMany('UserPlate’);
To return a collection of cars belonging to user $id you should be able to run:
$cars = User::findOrFail($id)-> user_plates->pluck('car');
Related
hello i'm trying to build school management system on secondary education and i have a ERM design i would Like to ask does laravel handle this type of relationship Many to many? please amend if i'm doing it wrongly since i'm a beginner thanks..
ERM
With 2 db tables many to many reationship
students(id,name,created_at,updated_at)
subjects(id, name, created_at,updated_at)
student_subjects(id, student_id, subject_id)
Models
class Student extends Model{
public function subjects(){
return $this->belongsToMany(Subject::class, 'student_subjects'); //here student_subjects is as a pivot table
}
}
class Subject extends Model{
public function stdents(){
return $this->belongsToMany(Student::class, 'student_subjects'); //here student_subjects is as a pivot table
}
}
Now Save data
$student = Student::find(1);
$student->subjects()->attach(2); // it will save subject 2 for student 1 in `student_subjects` table.
Note: similarly you can create relation for other models
For details check https://laravel.com/docs/5.6/eloquent-relationships#many-to-many
I have three tables:
users
columns: id, name
books
columns: id, name
book_user:
columns: user_id, book_id, state(not read yet, reading, read already)
I intended to user book_user as many-to-many relation table, so I follow the name convention from doc:
To define this relationship, three database tables are needed: users, roles, and role_user. The role_user table is derived from the alphabetical order of the related model names, and contains the user_id and role_id columns.
I wrote code:
class User extends Model
{
public function books()
{
return $this->belongsToMany('App\Book');
}
}
, and I can retrieve the books which related to the user by call user->books().
That works well, but when I try to retrieve the state of the book which related to a user, I create model:
class BookUser extends Model
{
//
}
When I use this Model, it claims:
Base table or view not found: 1146 Table 'myapp.book_users' doesn't exist
Conclusion:
the name convention of a table which can be used as many-to-many is <singular_noun>_<singular_noun> (such as book_user).
the name convention of table with multiple words which mapping to a Model is <singular_noun>_<plural_noun> (such as book_users).
I know I can set the table name manually which a model mappings to, but I just wonder:
Does that conflict is a design flaw or just I'm doing wrong in designing tables and models?
You don't need define a model for pivot table,just add withPivot
class User extends Model
{
public function books()
{
return $this->belongsToMany('App\Book')->withPivot('state');
}
}
Then you can retrieve book states from model pivot
Generally you don't need a model for pivot tables. You can define the inverse of the relationship. And if you want to store extra data in pivot table maybe you can check withPivot method. Or explain what are you trying to do.
But if you want to create a model, you need to specify your table name in your model manually. Because Laravel doesn't know if its a pivot table or normal table. It just tries to guess the table name by making it plural.
I need some help make a music library database.
I have 3 tables albums, artists, roles
I want an artist to have a role for each album.
like :
artist 1 work as Composer for album 1, but also work as arranger on album 2 or work as composer and arranger on album 3
I have tried this
how should database looks? and what type relationship is?
In your current schema, you will not be able to tag the role of the artist on basis of album.
As there is no relation in your tables to define that the entry in artist_role table is for specific album. So, what I would suggest is to create an intermediate table containing the role_id,artist_id and album_id.
To use this intermediate table with laravel's manyToMany relationship, you can define the methods in your models specifying one attribute as pivot attribute.
For, e.g. in Artist Model:
public function Roles(){
return $this->belongsToMany('App\Roles')->withPivot('album_id');
}
public function Albums(){
return $this->belongsToMany('App\Albums')->withPivot('role_id');
}
Define similar methods for other Models also..
Update:
For getting Artist with its role in Album add following method in the Album model:
public function Artists(){
return $this->belongsToMany('App\Artist')->withPivot('role_id');
}
For roles add following method:
public function Roles(){
return $this->belongsToMany('App\Roles')->withPivot('artist_id');
}
I'm trying to create a polymorphic relationship with multiple pivot tables. I have a table of requirements that can be assigned to accounts, roles, trips, and countries. This needs to be a many to many relationship because the same requirement could apply to multiple countries and/or trips and/or accounts etc.
I then need a table listing outstanding requirements for the user. For example: if a user has a certain account and there are requirements related to that account, then those requirements would be added to the user's list of requirements.
One solution I have is to first assign the requirements to the accounts, roles, trips, and countries using Pivot tables in a Many to Many relationship. Then using a polymorphic relationship I would connect the user to whichever pivot tables relate.
But I don't know how to do this or if it is even possible?
Here are my tables:
user_requirements
- id
- user_id
- requireable_id
- requireable_type
account_requirement
- id
- account_id
- requirement_id
role_requirement
- id
- role_id
- requirement_id
trip_requirement
- id
- account_id
- requirement_id
country_requirement
- id
- account_id
- requirement_id
Laravel 4.1 now has support for polymorphic many to many relationships.
Example below shows how I have implemented sharing Photos with both Products and Posts.
DB Schema
photos
id integer
filename string
alt string
photoable
id integer
photoable_id integer
photoable_type string
Models
Photo Model
class Photo extends Eloquent
{
public function products(){
return $this->morphedByMany('Product', 'photoable');
}
public function posts(){
return $this->morphedByMany('Post', 'photoable');
}
}
Product Model
class Product extends Eloquent
{
public function photos(){
return $this->morphToMany('Photo', 'photoable');
}
}
Post Model
class Post extends Eloquent
{
public function photos(){
return $this->morphToMany('Photo', 'photoable');
}
}
With the above, I can access all photos which are attached to a product as follows:
$product = Product::find($id);
$productPhotos = $product->photos()->all();
I can also iterate over to display all photos as any collection of models.
foreach ($productPhotos as $photo)
{
// Do stuff with $photo
}
The above can be replicated almost exactly to your requirements.
create a requirements table
create a requireable table
In Requirement model, declare all morphedByMany relationships
In Country, Trip, Role etc. declare morphToMany relationships
nb - I've typed this out freehand in S/O with no code editor, so there will probably be a typo, error or two - but concept remains the same.
A polymorphic relation in Laravel 4 is intended for single MODEL associations, therefore you cannot achieve what you are trying to build with this method. This is due to the fact that a pivot table doesn't represent a Model.
I have three tables: users, items and user_items. A user has many items and a item belongs to many users.
The tables:
Users
id
username
password
Items
id
name
equipable
User_items
id
user_id
item_id
equipped
The models:
class User extends Eloquent {
public function items()
{
return $this->belongsToMany('Item', 'user_items')
->withPivot('equipped');
}
}
class Item extends Eloquent {
public function users()
{
return $this->belongsToMany('User', 'user_items');
}
}
In the pivot (user_items) table I've a very important column named "equipped".
I've a form where users can equip, unequip and throw items. This form has a hidden field with the pivot (user_items) table row id. So, when a user tries to equip an item, the system checks if the item is equipable.
So, I want a object with the pivot data and the item data, based on item_id from the pivot table, I can send to the handler (where all logic is handled).
So what I've to do is to first access the pivot table and then access the item table.
Something like this (does not work):
$item = User::find(1)->items->pivot->find(1);
Is this possible to do?
You first have to include 'equipable' on your pivot call:
return $this->belongsToMany('User', 'user_items')
->withPivot('equipable');
Then you can ask Eloquent if your item is equipable or not:
$item = User::with('items')->get()->find(1)->items->find(2)->pivot->equipable;
Keep two things in mind:
Eloquent uses 'items' as a key internally, so that might interfere.
Whatever method you put before "get()" is part of the db query. Everything after "get()" is handled by PHP on the Object. The latter will be slower in most cases.