auto-injected Laravel model has no attributes

问题

I'm new to Laravel. I have created a model, a resource controller, and a route for one of my tables, I have modified the model class to use a particular table name, but the model object injected by Laravel 5.4 has no attributes even though a corresponding record exists in the database. Here are the steps I took.

1) Create the model with artisan. I ran this command:

php artisan make:model Tree

2) Modify the Tree model class as instructed to specify a specific table. I had to do this because my table is named tree, not the "trees" as Laravel would otherwise assume based on its internal rules.

/**
 * The table associated with the model.
 *
 * @var string
 */
protected $table = 'tree';

3) Create a resource controller that makes use of my model with this command

php artisan make:controller CategoryController --resource --model=Tree

4) Add a resource route routes/web.php in order to map a web server path onto the controller:

Route::resource('categories', 'CategoryController');

5) Modify the show() method of the CategoryController to var_dump the injected $tree object. It looks like this:

/**
 * Display the specified resource.
 *
 * @param  \App\Tree  $tree
 * @return \Illuminate\Http\Response
 */
public function show(Tree $tree)
{
    // we need to display the children of $tree
    var_dump($tree);

}

6) My table structure follows all the conventions specified by Laravel docs. There is an integer id column that is unsigned & auto-incrementing. I have the created_at and updated_at timestamps. The only thing different is that the table name is "tree" and not "trees", but that should be covered with the change I made above:

CREATE TABLE IF NOT EXISTS `tree` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `parent_id` int(10) unsigned DEFAULT NULL,
  `label` varchar(64) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '',
  `display_order` int(11) unsigned NOT NULL DEFAULT '0',
  `forum_id` int(5) NOT NULL DEFAULT '0',
  `url` varchar(128) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '',
  `flavor` tinyint(4) NOT NULL DEFAULT '0',
  `created_at` timestamp NULL DEFAULT NULL,
  `updated_at` timestamp NULL DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `parent_pkey` (`parent_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

This table contains data. It most definitely has a record with id=1.

7) I visit the url which should activate the show() method of my resource controller. The output I get verfies that this is in fact the method CategoryController::show(). http://example.com/categories/1

Here is the problem.

The output of var_dump($tree) has no attributes. There is no error, but something is wrong with the injected object.

object(App\Tree)#217 (24) {
  ["table":protected]=>
  string(4) "tree"
  ["connection":protected]=>
  NULL
  ["primaryKey":protected]=>
  string(2) "id"
  ["keyType":protected]=>
  string(3) "int"
  ["incrementing"]=>
  bool(true)
  ["with":protected]=>
  array(0) {
  }
  ["perPage":protected]=>
  int(15)
  ["exists"]=>
  bool(false)
  ["wasRecentlyCreated"]=>
  bool(false)
  ["attributes":protected]=>
  array(0) {
  }
  ["original":protected]=>
  array(0) {
  }
  ["casts":protected]=>
  array(0) {
  }
  ["dates":protected]=>
  array(0) {
  }
  ["dateFormat":protected]=>
  NULL
  ["appends":protected]=>
  array(0) {
  }
  ["events":protected]=>
  array(0) {
  }
  ["observables":protected]=>
  array(0) {
  }
  ["relations":protected]=>
  array(0) {
  }
  ["touches":protected]=>
  array(0) {
  }
  ["timestamps"]=>
  bool(true)
  ["hidden":protected]=>
  array(0) {
  }
  ["visible":protected]=>
  array(0) {
  }
  ["fillable":protected]=>
  array(0) {
  }
  ["guarded":protected]=>
  array(1) {
    [0]=>
    string(1) "*"
  }
}

Have I done something wrong? How do I get Laravel to inject the correct object?

EDIT: Someone asked why I was injecting the wrong object in my route. Here is an abbreviated version of the class that was auto-generated in step #3. It clear references the Tree class and code-hints it is expecting a tree object. I did not create any of this code except the var_dump statement. It was all auto-generated by artisan commands expressly as instructed by the docs.

namespace App\Http\Controllers;

use App\Tree;
use Illuminate\Http\Request;

class CategoryController extends Controller
{

    /**
     * Display the specified resource.
     *
     * @param  \App\Tree  $tree
     * @return \Illuminate\Http\Response
     */
    public function show(Tree $tree)
    {
        // we need to display the children of $tree
        var_dump($tree);

    }

}

回答1:

There is a naming convention on Route Model binding.

Try to change the action call to this:

public function show(Tree $category)
{
    var_dump($category);
}

Update: I looked in the source and you can also change the parameters name in resource Route declaration:

Route::resource('categories', 'CategoryController', ['parameters'=>['categories'=>'tree']]);

And use the $tree variable in action call

public function show(Tree $tree)

回答2:

The issue comes in the resource routing. Replace your routing as

Route::resource('category', 'CategoryController');

Here the route name must exactly match with the controller name. That was the problem.

回答3:

I also run into this problem. Laravel will follow the convention for naming the parameter.

For example your model is

AwesomeCategory

Then auto-generated edit method in AwesomeCategoryController will look like this

public function edit(AwesomeCategory $awesomeCategory) // This will not load any attributes

Change to

public function edit(AwesomeCategory $awesomecategory) // This will be automatically loaded with all attributes

来源：https://stackoverflow.com/questions/42543124/auto-injected-laravel-model-has-no-attributes