[Proposal]: Model Arguments

[myckhel]

This is a proposed method to fix some limitations with eloquent models which some dynamic variables cannot be used with models relationships and attribute retrievals.

Given the below specifications:

• calculate distance between each models and the authenticated user
• assign each distance result to each models attribute as distance

Using normal way

User.php

  // User.php
  // function to calculate distance between models coordinates and the given coordinates
  function getDistance($latitudeTo, $longitudeTo, $earthRadius = 6371000) {
    $latFrom = $this->lat;
    $lonFrom = $this->lng;
    if (!$latFrom || !$lonFrom && !$latitudeTo || !$longitudeTo) {
      return null;
    }
    $latitude = $latitudeTo ?? 0;
    $longitude = $longitudeTo ?? 0;
    $calc = 1.1515 * 1.609344;

    return ROUND(
      (
        ACOS(
          SIN($latitude * PI() / 180)
          * SIN($latFrom * PI() / 180)
          + COS($latitude * PI() / 180)
          * COS($latFrom * PI() / 180)
          * COS(($longitude - $lonFrom) * PI() / 180)
        ) * 180 / PI()
      ) * 60 * $calc,
      2
    );
  }

Retrieving users with calculated distance from auth user

// UserController.php
function index(Request $request){
  $authUser = $request->user(); // {id, name, lat, lng}
  
  $users = User::get(); // [{id, name, lat, lng}]
  
  $users->map(function ($user) use($authUser){
    $user->distance = getDistance($authUser->lat, $authUser->lng);
  });
  
  return $users; // [{id, name, lat, lng, distance}]
}

function show(Request $request, User $user){
  $authUser = $request->user(); // {id, name, lat, lng}
 
  $user->distance = getDistance($authUser->lat, $authUser->lng);
  
  return $users; // [{id, name, lat, lng, distance}]
}

we could improve above approach by using laravel getAttribute feature.

with this approach no way to pass the authenticated user coordinates to the getDistanceAttribute

User.php

// User.php
function getDistanceAttribute() {
  // $authUser object cannot be retrieved
  return  $this->getDistance($authUser->lat, $authUser->lng);
}

That is when model argument feature can come in.

// HasArgAttribute.php
trait HasArgAttribute
{

  protected $args = [];

  // function to populate the models args with values
  function setArgs(array $args) {
    $this->args = $args;
    
    return $this;
  }

  // function to make `args` available for model query builder
  function scopeWithArgs($q, $args, callable $call = null) {
    // when model retrieved
    static::retrieved(function ($model) use($args, closure $call) {
      // set the model args
      $model->setArgs($args);
      
      $call && $call($model);
    });
  }
}

we could use HasArgAttribute to pass coordinates to the user model.

  // User.php
use HasArgAttribute;

function getDistanceAttribute() {
  // we should expect args to be populated with some value(s).
  
  if (!$this->args) {
    return null;
  }
  
  return $this->getDistance($this->args[0], $this->args[1]);
}

Retrieving users with calculated distance from auth user using HasArgAttribute

// UserController.php
function index(Request $request){
  $authUser = $request->user(); // {id, name, lat, lng}
  
  $users = User::withArgs(
            [$authUser->lat, $authUser->lng],
            fn ($model) => $model->setAppends(['distance'])
          )->get(); // [{id, name, lat, lng, distance}]
  
  return $users; // [{id, name, lat, lng, distance}]
}

function show(Request $request, User $user){
  $authUser = $request->user(); // {id, name, lat, lng}
 
  $user->setArgs([$authUser->lat, $authUser->lng]);
  
  $user->setAppends(['distance']);
  
  return $user; // {id, name, lat, lng, distance}
}

same feature could be used with relationships

// User.php
function posts() {
  // allows us to use dynamic relationship key
  // currently not possible without model args feature
  return $this->hasMany(Post::class, $this->args['some_dynamic_value']);
}

Please could this be a useful feature in the laravel framework? @themsaid and everyone else.