I have a problem creating a "Double" n:m relation in Laravel.
First I have two tables called locations and services. These tables have a n:m relation and a table called location_service. The table has an incremental id and an id of each table.
In the Models I have the following Code:
class Service extends Model
{
public function locations(){
return $this->belongsToMany('app\Location','location_service','service_id','location_id');
}
}
class Location extends Model
{
public function services(){
return $this->belongsToMany('app\Service','location_service','location_id','service_id');
}
}
In addition, I created a table called tags. This table tag can be linked to several location_service and several location_service can be linked to different tags. I created a table called location_service_tag with an incremental id, the id of the location_service and the id of the tag. But how should I do the model? The point is, that there is no Model like app\Location_Service.
Related
I have two migration tables and two models
1)User.
2)Subscription.
in subscriptions Model i write one method called user() which has hasMany relationship and in Users model it will contain subscriptions() method which have belongs() relationship.
in user table id acts as an primary key and in subscription table sub_id acts as a foriegn key,for example if the user subscribed to any subscription the user id will store in the sub_id in the subscription table upto this it's working fine.
$is_subscription=Subscription::where('sub_id',$user->id)->value('sub_id');
from the above code i am able to get the value but now what i want is is there any better way to write the query based on models ,please help me to write this one..
According to your descriptions, I believe this is what you have:
class User extends Model
{
public function subscriptions()
{
return $this->hasMany(Subscription::class);
}
}
class Subscription extends Model
{
public function user()
{
return $this->belongsTo(User::class);
}
}
So you want to check whether an user has any subscriptions. You can do one of the followings:
$user->subscriptions()->exists();
// Or
$user->subscriptions->isNotEmpty();
You can use pluck() method:
$is_subscription=Subscription::where('sub_id',$user->id)->pluck('sub_id');
You can find details on the methods that are available for collection using the Laravel Documentation
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 am using laravel 5.1. The scenario is as follows(this is an example. The real scenario is similar to this example)
I have 3 models
College
Student
Teacher
A college can have many students but a student can belong to only 1 college.
A college can have many teachers but a teacher can belong to only 1 college.
I want to establish relationships between these tables in laravel.
One of the methods for this is to place a college_id foreign key on the Students and Teachers table. But in my case, this foreign key will be null a lot of times. So rather than have separate columns in 3-4 tables with mostly null values, I wanted to explore the option of having a polymorphic relationship for College table.
This is what I tried:
The example given in the laravel docs(link below) depict a one-to-many relationship whereas my scenario is more of a many to one relationship.
http://laravel.com/docs/5.1/eloquent-relationships#polymorphic-relations
As given in the example, having collegeable_id and collegeable_type columns on the College table would not have fulfilled my requirement as a college can contain many students/teachers so I created a pivot table:
Schema::create('collegeables', function (Blueprint $table) {
$table->integer('college_id')->unsigned();
$table->integer('collegeable_id')->unsigned();
$table->string('collegeable_type');
});
And I have the following models
College Model:
namespace App;
use Illuminate\Database\Eloquent\Model;
class College extends Model
{
public function students()
{
return $this->morphedByMany('App\Student', 'collegeable');
}
}
Student Model:
namespace App;
use Illuminate\Database\Eloquent\Model;
class Student extends Model
{
public function college()
{
return $this->morphOne('App\Colleges', 'collegeable');
}
}
With this arrangement, I am able to store students using College model instance like this
$college = \App\College::find(1);
$student = new \App\Student;
$student->name = 'John Doe';
$college->students()->save($student);
But when I try to retrieve a College model instance using a student model instance as specified below, it gives me an error:-
public function index()
{
return \App\Student::find(1)->college;
}
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'colleges.collegeable_id'
This is kind of expected as morphOne works with columns in a table I suppose.
If I change the morphOne function in Student Model to morphToMany, the code starts working and I am able to retrieve values as well. But that make this relationship a many to many which again is not what I want.
So my question is this:-
Is their a morphSomething function I can use in the student model to be able to retrieve values for the student's college while maintaining the relationship as a one-to-many?
Any help would be really appreciated. Thanks.
There's no reason to use Polymorphic relationships here. Instead, just add a foreign key to your colleges table on both your students and teachers tables. Like this:
colleges
id
name
teachers
id
name
college_id
students
id
name
college_id
Then your models can use the belongsTo() and hasMany() relations, like so:
class College extends Model {
public function students() {
return $this->hasMany(App\Student::class);
}
public function teachers() {
return $this->hasMany(App\Teacher::class);
}
}
class Teacher extends Model {
public function colleges() {
return $this->belongsTo(App\College::class);
}
}
class Student extends Model {
public function colleges() {
return $this->belongsTo(App\College::class);
}
}
Polymorphic one-to-many relations are for the opposite of this relationship where you have a model that can only be related to a single record, but that record can be many different models.
Edit: To further explain why a polymorphic relationship isn't needed here, let's take a look at where it would be needed. Say you have a simple CRM style website. There are Customers and Projects and you want to have Comments on both. In this case, you would make Comments a polymorphic relationship because Comments belong to a single Customer or a single Project, but not both.
Your relationship is the exact opposite. In your case, Students and Teachers belong to a college. If you were to follow the previous example's pattern, a college would have belonged to a single student or teacher.
I had a similar need and managed to improvise in another way, taking advantage of morph's table structure.
You will need a Collegeable class to be Pivot (https://laravel.com/docs/9.x/eloquent-relationships#defining-custom-intermediate-table-models)
And then the magic:
public function college(){
return $this->hasOneThrough(Colleges::class,
Collegeable::class,
'collegeable_id',
'id',
'id',
'college_id',
);
}
And on the Collegeable Pivot class:
namespace App\Models;
use Illuminate\Database\Eloquent\Relations\Pivot;
class Collegeable extends Pivot
{
protected $table = 'collegeables';
}
So, I've been trying to watch and read eloquent relationships from laracasts. Unfortunately I still don't quite get how to translate database relationships to eloquent relationships (hasOne, belongsTo, hasMany, etc).
Let's say I have an Account and Customer tables. Account table has a "Customer_id" foreign key which references to the "id" on Customer table. Let's assume it's a one-to-many relationship. How should I put it on my models on laravel?
Which table should contain the "hasMany" and which one should have the "belongsTo"?
Just think about how you would say it. In your case it sounds like a Customer has many Accounts and an Account belongs to one Customer.
So you would put the hasMany() in your Customer model and the belongsTo() in your Account model.
class Customer extends Model {
public function accounts() {
return $this->hasMany('App\Account');
}
}
class Account extends Model {
public function customer() {
return $this->belongsTo('App\Customer');
}
}
You can read more about Laravel database relationships here.
I couldn't get related models in many-to-many polymorphic relation saved into database.
$photo = Photo::find(1);
$photo->articles()->attach(2);
something like this wouldn't work and gives
error: Call to undefined method
Illuminate\Database\Query\Builder::articles()'
How to do it the right way?
Models
class Tag extends Eloquent
{
public function articles()
{
return $this->morphedByMany('Article', 'taggable');
}
public function photos()
{
return $this->morphedByMany('Photo', 'taggable');
}
}
class Article extends Eloquent
{
public function tags()
{
return $this->morphToMany('Tag', 'taggable');
}
}
class Photo extends Eloquent
{
public function tags()
{
return $this->morphToMany('Tag', 'taggable');
}
}
Finally got it working... Basically it's polymorphism + many to many relationship combined. I thought it don't require tags table. Taggables table acts as pivot table and tags is the table which contains Tag objects that connect models based on pivot table (taggables table)
Morphing does not Support Many To Many, it is actually a one to one association, it is used to create relations between different Models, so for example if you have Tag Model, the tag model could relate to many different occasions, it could relate to Page Model, to Post Model, to Product Model etc, what it actually achieves is that it allows you to relate to that other model without explicity defining the related model in the DB level, for instance a Tag model could be associated with a Post Model, but then you would need to define in the db, a post_id foreign key, with Polymorphic relations you can relate to that Post Model, without defining the model on the DB level as a specific field:
Polymorphic relations allow a model to belong to more than one other model, on a single association
And in Django Documentation you can clearly see how this association works:
staff
id - integer
name - string
orders
id - integer
price - integer
photos
id - integer
path - string
imageable_id - integer
imageable_type - string
The association from above is: 1 Photo relates to 1 Other Model, but with a different concrete implementation* thus a photo can belong to Staff, or it can belong to an order.