如何在不获取模型内容的情况下从相关模型附加 Eloquent 属性？

Question

I have 2 eloquent models:

EloquentUser

and

SharedEvents

They are both related by user_id

I'm attempting to set up and appends attribute in the SharedEvents model that will append the full_name of the user with whom the event has been shared.

For the sake of readability, I'm only including the appends components of my class

class SharedEvents extends Model {

protected $appends      = ['fullName'];

/**
 * @return BelongsTo
 */
public function user() : BelongsTo {
    return $this->belongsTo('Path\To\EloquentUser', 'shared_with_id', 'user_id');
}

    /**
 * @return mixed
 */
public function getFullNameAttribute(){
    return $this->user->user_full_name;
}

Unfortunately when I run this I'm getting back both the full name and the entire user model when I only want the full name.

Is there a way to avoid attaching the content of the user model?

Answer 1

It feels like you're trying to make columns from your EloquentUser model first class citizens in your SharedEvent model. You're getting close, but consider...

When working with relationships, this is a good way to be explicit:

Assuming user_full_name is an accessor on your User model:

// EloquentUser.php

// This will automatically add your accessor to every query 
// as long as you select the columns the accessor is made 
// up of
protected $appends = ['user_full_name'];

/**
 * User Full Name Accessor

 * @return string
 */
public function getUserFullNameAttribute()
{
    return $this->first_name . ' ' . $this->last_name;
}

// SharedEvent.php

/**
 * A SharedEvent belongs to an Eloquent User

 * @return BelongsTo
 */
public function user() : BelongsTo 
{
    return $this->belongsTo('Path\To\EloquentUser', 'shared_with_id', 'user_id');
}

// Somewhere in your controller or wherever you want to access the data
$sharedEvents = SharedEvent::with(['user' => function ($query) {
    $query->select('user_id', 'first_name', 'last_name');
}])->where(...)->get(['shared_with_id', ...other columns]); // you must select the related column here

This should get you the closest to what you want, but there are a couple of things you should know:

1. If user_full_name is an accessor, you need to select all of the columns that make up that accessor (as I mention above)
2. You must select the related keys ( user_id in EloquentUser and shared_with_id in SharedEvent )
3. The $appends is necessary in EloquentUser here because you can't directly add an accessor to your sub query inside the closure.

Try to get comfortable with using a closure as the 2nd argument in your relationships. It's the best way to really be precise as to which columns you're selecting when you're loading relationships — Eloquent makes it really easy to be lazy and just do:

SharedEvent::with('user')->get();

which as you've see will just do a select * on both SharedEvent and your user relationship.

Another thing I've noticed when working with complex queries that use relationships is that you can quickly reach a point where it feels like you're fighting the framework. That's often a sign to consider simplifying ot just using raw SQL. Eloquent is powerful, but is just another tool in your programming tool belt. Remember that you have other tools at your disposal.

Answer 2

I was running into the same problem, and my first idea was to explicitly hide the (entire) associated model when fetching SharedEvent .

In your case, this would look like:

class SharedEvents extends Model {

   protected $appends  = ['fullName'];
   protected $hidden   = ['user'];
   ...
}

I actually decided against this since I am returning a lot of other attached models, so I decided on attaching the entire user, but I tested it and it works.

FYI, I'm not sure if the discrepancy is due to an older version of Laravel, but Eloquent actually expects $appends attributes to be in snake-case ( https://laravel.com/docs/5.6/eloquent-serialization#appending-values-to-json ):

Note that attribute names are typically referenced in "snake case", even though the accessor is defined using "camel case"

Answer 3

Can you try this?

public function user() : BelongsTo {
    return $this->belongsTo('Path\To\EloquentUser', 'shared_with_id', 'user_id')->select('fullName','user_id');
}

Answer 4

After doing some research and experimentation, it doesn't look like there's a way to do this with Eloquent. The solution I ended up going with unfortunately is running an additional query.

/**
 * This is inefficient, but I could not find a way to get the full name
 * attribute without including all of user.
 *
 * @return string
 */
public function getFullNameAttribute(){
    return EloquentUser::select('user_full_name')
                        ->where('user_id', $this->shared_with_id)
                        ->first()
                        ->user_full_name;
}