Need to set a 1 to many relationship in the same table in Laravel 4

问题

I have the following models

Category:

<?php

class Category extends Eloquent {
    protected $table = "category";
    protected $fillable = array('title','parent','metatit','metadsc','metake','metaurl','image');
    public function categoryitems(){
        return $this->hasMany('CategoryItem','catid');
    }
    public function parent(){
        return $this->hasMany('category','parent');
    }
    public function child(){
        return $this->belongsTo('Category','parent');
    }
}

Need to set a 1 to many relationship in the category table Ex category "cities" is a child of category "countries"

the error happen when i try to use the following code

<?php

$parent = Category::where('id','=',$cat->id)->parent;
echo $parent->title;

?>

The error :

ErrorException (E_UNKNOWN) Undefined property: Illuminate\Database\Eloquent\Builder::$parent (View: /var/www/phpWithAngulerJS/app/views/admin/category-edit.blade.php)

回答1:

First off, fix the relations as follows:

public function children() {
    return $this->hasMany('Category','parent');
}
public function parent() {
    return $this->belongsTo('Category','parent');
}

And your query needs to be executed first:

$parent = Category::where('id','=',$cat->id)->first()->parent;
// btw since you have $cat, you probably can do simply:
$cat->parent;

echo $parent->title;

来源：https://stackoverflow.com/questions/28930251/need-to-set-a-1-to-many-relationship-in-the-same-table-in-laravel-4