Handling mapping table in laravel eloquent - php

Question

In my application, there will be multiple investors tagged for single purchase entry. So on loading a purchase entry, I should get all the investors associated.
In my controller,
return response()->json(GoldPurchase::with('investors')->get());
Mapping table schema,
Schema::create('gold_purchase_investor', function (Blueprint $table) {
$table->increments('id');
$table->integer('investor_id')->unsigned();
$table->integer('purchase_id')->unsigned();
$table->timestamps();
$table->foreign('investor_id')
->references('id')
->on('investors')
->onDelete('cascade');
$table->foreign('purchase_id')
->references('id')
->on('gold_purchases')
->onDelete('cascade');
});
Purchase model,
class GoldPurchase extends Model
{
public function investors() {
return $this->hasMany('App\GoldPurchaseInvestor');
}
}
Investor model,
class Investor extends Model
{
protected $fillable = ['name', 'address', 'mobile', 'email'];
public function purchases() {
return $this->hasMany('App\GoldPurchase');
}
}
PurchaseInvestor model,
class GoldPurchaseInvestor extends Model
{
protected $table = 'gold_purchase_investor';
public function purchase() {
return $this->belongsTo('App\GoldPurchase');
}
public function investor() {
return $this->belongsTo('App\Investor');
}
}
With this, I am getting error,
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'gold_purchase_investor.gold_purchase_id' in 'where clause' (SQL: select * from `gold_purchase_investor` where `gold_purchase_investor`.`gold_purchase_id` in (1))

Answer 1

You have to specify the custom foreign key:
public function investors() {
return $this->hasMany('App\GoldPurchaseInvestor', 'purchase_id');
}
But this is actually a case for a BelongsToMany relationship:
public function investors() {
return $this->belongsToMany('App\Investor', 'gold_purchase_investor', 'purchase_id');
}

Answer 2

From the Eloquent Relationship:
Remember, Eloquent will automatically determine the proper foreign key column on the Comment model. By convention, Eloquent will take the "snake case" name of the owning model and suffix it with _id. So, for this example, Eloquent will assume the foreign key on the Comment model is post_id.
$this->hasMany('App\Comment', 'foreign_key', 'local_key');
So try to write your foreign key and local key in the relationships
In your case I think it would be something like that:
class GoldPurchase extends Model`
{
public function investors() {
return $this->hasMany('App\GoldPurchaseInvestor', 'investor_id', 'id');
}
}

Answer 3

Use belongsToMany for many-to-many relationships.
GoldPurchase.php
class GoldPurchase extends Model{
public function investors() {
return $this->belongsToMany('App\Investor','gold_purchase_investor','purchase_id','investor_id');
}
}
Investor.php
class Investor extends Model{
protected $fillable = ['name', 'address', 'mobile', 'email'];
public function purchases() {
return $this->belongsToMany('App\GoldPurchase','gold_purchase_investor','investor_id','purchase_id');
}
}
You don't need a third model for pivot table at all.
GoldPurchaseInvestor is not at all needed.