Laravel eloquent - 与不同表的一对一关系

Question

I have three tables,

1. user (id, name)
2. state (id, stateName, code)
3. user_relations(id, user_id, state_id)

3 models,

1. User
2. State 
3. UserRelation

By logic, User has one UserRelation and UserRelation has one State

I can get user state by

User::first()->relation->state

What I want is call this by User::with('state')->first() .

Answer 1

If you would like to keep the current db schema like it is, you may use Laravel accessors

Accessors and mutators allow you to format Eloquent attribute values when you retrieve or set them on model instances.

class User

public function getStateAttribute($value) {
   return $this->relation->state;
}

Usage

User::findOrFail($id)->state;

Edit

User Model

class User extends Authenticatable
{
    //...

    public function state() {
        return $this->relation()->with('state');
    }


    public function relation() {
        return $this->hasOne('App\UserRelation', 'user_id');
    }

}

UserRelation Model

class UserRelation extends Model
{
    protected $table = 'user_relations';


    public function state() {

        return $this->belongsTo('App\State'); // must be belongsTo instead of hasOne
    }

}

State Model

class State extends Model
{
    protected $table = 'states';
}

Controller

App\User::with('state')->find(1);

{
  "id": 1,
  "name": "Test",
  "email": "test@test.com",
  "email_verified_at": "2020-02-13 00:00:00",
  "created_at": "2020-02-20 00:00:00",
  "updated_at": null,
  "state": {
    "id": 2,
    "state_id": 2,
    "user_id": 1,
    "state": {
      "id": 2,
      "stateName": "state 2",
      "code": "code 2"
    }
  }
}

Answer 2

If user can only have one state,

add a state_id in the user table and get rid of the third table user_relations

class User extends Model
{
    public function state()
    {
        return $this->hasOne('App\State');
    }
}

class State extends Model
{
    public function user()
    {
        return $this->belongsTo('App\User');
    }
}

In this way, you can

$state = User::find(1)->state;
$user = State::find(1)->user;

Answer 3

If you are doing one-to-one relationship you won't need a pivot table, in your case the user_relations table. Pivot tables are used to express many-to-many relations.

And for the solution you want. You will have to store the user_id in the state table. so your state table should look like the following:

state (id, user_id, stateName, code)

Relations should be like:

User model:

public function state()
{
    return $this->hasOne('App\State');
}

State model:

public function user()
{
    return $this->belongsTo('App\User');
}

Answer 4

First way:

You have to define state_id in users table for one to one relation.

class User extends Model
{
    public function state()
    {
        return $this->hasOne('App\State');
    }
}

Or if you need same database structure, then

Second Way:

Basically it's Many to Many relations between User and State .

So better way is to define many to many relation function in Models of User and State considering UserRelation a middle(pivot) table.

class User extends Model
{
    public function states()
    {
        return $this->belongsToMany('App\State', 'user_relations');
    }
}

class State extends Model
{
    public function users()
    {
        return $this->belongsToMany('App\User', 'user_relations');
    }
}

and then to access states of user, you can call:

$user->states->first();

It's ok that you need one to one relation, you can call first() method to fetch first record od state.

Simillery to access user of state

$state->users->first();

And if you need to access user_relations (one to one) only, you have to define methods in both user and state model:

class User extends Model
{
    public function user_relation()
    {
        return $this->hasOne('App\UserRelation');
    }
}

class State extends Model
{
    public function user_relation()
    {
        return $this->hasOne('App\UserRelation');
    }
}

Answer 5

Since user and state are many to many, you can user belongsToMany function inside User model.

public function states(){
    return $this->belongsToMany(State::class, 'user_relations', 'user_id', 'state_id');
}

You can get Eager Loading by retrieving both models related to the user like:

$user = User::with('states')->first();

And now to retrieve states, you can loop through the states like:

foreach($user->states as $state){
    //Retrieved state model variable
    ....
}