How to get a value from a three-level depth relation in Laravel using Eloquent?

Question

I have 3 tables as below:

Users Table (has only one phone):

id	Name	phone_id
1	Sam	1
2	Tom	2

/**
* @return HasOne
*/
public function phone()
{
    return $this->hasOne(phones::class);
}

/**
* @return ???
*/
public function key()
{
    return ???;
}

Phone Table (has only one key):

id	Name	key_id
1	Nokia	1
2	Samsung	2

/**
* @return HasOne
*/
public function key()
{
    return $this->hasOne(keys::class);
}

Key Table:

id	Name
1	asd123
2	qwe345

/**
* @return belongTo
*/
public function phone()
{
    return $this->belongTo(phones::class);
}

I wanted to know how to get the key from the user model:

User::find(1)->key()->Name

Do you have any **specific** question about this? Anything not working? Also, how would you define the "best relation"? — Nico Haase, Oct 24 '22 at 18:20
any specific question about this? Anything not working? Also, how would you define the "best relation" 1: How to get key from user model. 2: I do not know how to get key from user model. 3: corrected — buczo, Oct 24 '22 at 19:01

didene tahi · Accepted Answer · 2022-10-24T19:03:47.280

1

you need to work around hasOneThrough to get what you need.

let's break it down, based on your schema:

a User belongs to one Phone
a phone belongs to Key
therefore, a User belongs to Key through Phone

making this clear, we need to declare our key relationship inside the User model:

public function key()
{
    return $this->hasOneThrough(
        Key::class,       // model we are trying to get
        Phone::class,      // model we have an _id to
        'id',                 // WHERE `phone`.`id` = `user`.`phone_id`
        'id',                 // `key`.`id`
        'phone_id',        // local column relation to our through class
        'key_id'          // `phone`.`key_id`
    );
}

this will get you directly key from user

edited Oct 24 '22 at 19:03

answered Oct 24 '22 at 18:31

didene tahi

420
3
7

hasOneThrough() cannot be used in this case as I do not store phone_id on keys model. – buczo Oct 24 '22 at 18:44
@buczo i have updated my answer entirely, i think this should work. – didene tahi Oct 24 '22 at 19:05
Yes that's work as expected! Awesome! – buczo Oct 24 '22 at 19:10
notice that there's a package that you can add, to use `belongsToThrough` directly, without writing this method everytime. https://github.com/staudenmeir/belongs-to-through – didene tahi Oct 24 '22 at 19:15
note than you need to use `belongsTo` instead of `hasOne` in the first two mentioned relationships. – didene tahi Oct 24 '22 at 19:23

score 0 · Answer 2 · answered Oct 24 '22 at 19:11

Since a user can have only one phone (as mentioned) and phone has one key you have to use hasOneThrough() relation in model A.

Functions:

Public function getKey()
{
    Return $this->hasOneThrough(‘App\Models\Keys’, ‘App\Models\Phone’, ‘foreignKey on Phones’, ‘foreignKey on Keys’);
}

Note: For this to work you have to pick top to down approach so make migrations like this User->Phones->Keys.

There is another package that allow belongsToThrough i think its called haven’t used it tho if you want to look into reverse relation lookup (idk why someone need that :))

How to get a value from a three-level depth relation in Laravel using Eloquent?

2 Answers2