Support table aliases

README.md

@@ -81,6 +81,37 @@ class Comment extends Model
 }
 ```
 
+### Table Aliases
+
+If your relationship path contains the same model multiple times, you can specify a table alias (Laravel 6+):
+
+```php
+class Comment extends Model
+{
+    use \Znck\Eloquent\Traits\BelongsToThrough;
+
+    public function grandparent()
+    {
+        return $this->belongsToThrough(
+            'App\Comment',
+            'App\Comment as alias', 
+            null,
+            '',
+            ['App\Comment' => 'parent_id']
+        );
+    }
+}
+```
+
+Use the `HasTableAlias` trait in the models you are aliasing:
+
+```php
+class Comment extends Model
+{
+    use \Znck\Eloquent\Traits\HasTableAlias;
+}
+```
+
 ### Soft Deleting
 
 By default, soft-deleted intermediate models will be excluded from the result. Use `withTrashed()` to include them:

src/Relations/BelongsToThrough.php

@@ -89,15 +89,13 @@ protected function performJoins(Builder $query = null)
         $query = $query ?: $this->query;
 
         foreach ($this->throughParents as $i => $model) {
-            $table = $model->getTable();
-
             $predecessor = $i > 0 ? $this->throughParents[$i - 1] : $this->related;
 
-            $first = $table.'.'.$this->getForeignKeyName($predecessor);
+            $first = $model->qualifyColumn($this->getForeignKeyName($predecessor));
 
             $second = $predecessor->getQualifiedKeyName();
 
-            $query->join($table, $first, '=', $second);
+            $query->join($model->getTable(), $first, '=', $second);
 
             if ($this->hasSoftDeletes($model)) {
                 $this->query->whereNull($model->getQualifiedDeletedAtColumn());
@@ -113,7 +111,7 @@ protected function performJoins(Builder $query = null)
      */
     protected function getForeignKeyName(Model $model)
     {
-        $table = $model->getTable();
+        $table = explode(' as ', $model->getTable())[0];
 
         if (array_key_exists($table, $this->foreignKeyLookup)) {
             return $this->foreignKeyLookup[$table];

src/Traits/BelongsToThrough.php

@@ -33,8 +33,7 @@ public function belongsToThrough($related, $through, $localKey = null, $prefix =
                 $model = $model[0];
             }
 
-            /** @var \Illuminate\Database\Eloquent\Model $instance */
-            $instance = new $model;
+            $instance = $this->belongsToThroughParentInstance($model);
 
             if ($foreignKey) {
                 $foreignKeys[$instance->getTable()] = $foreignKey;
@@ -54,6 +53,26 @@ public function belongsToThrough($related, $through, $localKey = null, $prefix =
         return $this->newBelongsToThrough($relatedInstance->newQuery(), $this, $throughParents, $localKey, $prefix, $foreignKeys);
     }
 
+    /**
+     * Create a through parent instance for a belongs-to-through relationship.
+     *
+     * @param string $model
+     * @return \Illuminate\Database\Eloquent\Model
+     */
+    protected function belongsToThroughParentInstance($model)
+    {
+        $segments = preg_split('/\s+as\s+/i', $model);
+
+        /** @var \Illuminate\Database\Eloquent\Model $instance */
+        $instance = new $segments[0];
+
+        if (isset($segments[1])) {
+            $instance->setTable($instance->getTable().' as '.$segments[1]);
+        }
+
+        return $instance;
+    }
+
     /**
      * Instantiate a new BelongsToThrough relationship.
      *

src/Traits/HasTableAlias.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Znck\Eloquent\Traits;
+
+use Illuminate\Support\Str;
+
+trait HasTableAlias
+{
+    /**
+     * Qualify the given column name by the model's table.
+     *
+     * @param string $column
+     * @return string
+     */
+    public function qualifyColumn($column)
+    {
+        if (Str::contains($column, '.')) {
+            return $column;
+        }
+
+        $table = $this->getTable();
+
+        if (Str::contains($table, ' as ')) {
+            $table = explode(' as ', $table)[1];
+        }
+
+        return $table.'.'.$column;
+    }
+}

tests/BelongsToThroughTest.php

@@ -50,6 +50,13 @@ public function testLazyLoadingWithDefault()
         $this->assertFalse($country->exists);
     }
 
+    public function testLazyLoadingWithAlias()
+    {
+        $comment = Comment::find(35)->grandparent;
+
+        $this->assertEquals(33, $comment->id);
+    }
+
     public function testEagerLoading()
     {
         $comments = Comment::with('country')->get();

tests/Models/Comment.php

@@ -2,8 +2,12 @@
 
 namespace Tests\Models;
 
+use Znck\Eloquent\Traits\HasTableAlias;
+
 class Comment extends Model
 {
+    use HasTableAlias;
+
     public function country()
     {
         return $this->belongsToThrough(Country::class, [User::class, Post::class])->withDefault();
@@ -25,6 +29,11 @@ public function countryWithPrefix()
         return $this->belongsToThrough(Country::class, [User::class, Post::class], null, 'custom_');
     }
 
+    public function grandparent()
+    {
+        return $this->belongsToThrough(self::class, self::class.' as alias', null, '', [self::class => 'parent_id']);
+    }
+
     public function user()
     {
         return $this->belongsToThrough(User::class, Post::class);

tests/TestCase.php

@@ -59,6 +59,7 @@ protected function migrate()
             $table->increments('id');
             $table->unsignedInteger('post_id')->nullable();
             $table->unsignedInteger('custom_post_id')->nullable();
+            $table->unsignedInteger('parent_id')->nullable();
         });
     }
 
@@ -84,11 +85,11 @@ protected function seed()
         Post::create(['id' => 23, 'user_id' => 13, 'custom_user_id' => null]);
         Post::create(['id' => 24, 'user_id' => null, 'custom_user_id' => 11]);
 
-        Comment::create(['id' => 31, 'post_id' => 21, 'custom_post_id' => null]);
-        Comment::create(['id' => 32, 'post_id' => 22, 'custom_post_id' => null]);
-        Comment::create(['id' => 33, 'post_id' => 23, 'custom_post_id' => null]);
-        Comment::create(['id' => 34, 'post_id' => null, 'custom_post_id' => 21]);
-        Comment::create(['id' => 35, 'post_id' => null, 'custom_post_id' => 24]);
+        Comment::create(['id' => 31, 'post_id' => 21, 'custom_post_id' => null, 'parent_id' => null]);
+        Comment::create(['id' => 32, 'post_id' => 22, 'custom_post_id' => null, 'parent_id' => null]);
+        Comment::create(['id' => 33, 'post_id' => 23, 'custom_post_id' => null, 'parent_id' => null]);
+        Comment::create(['id' => 34, 'post_id' => null, 'custom_post_id' => 21, 'parent_id' => 33]);
+        Comment::create(['id' => 35, 'post_id' => null, 'custom_post_id' => 24, 'parent_id' => 34]);
 
         Model::reguard();
     }