Example analysis of polymorphic Association usage of laravel 5.1 framework model

This paper illustrates the usage of polymorphic Association in laravel 5.1 framework model. Share with you for your reference, as follows:

What is polymorphic association? You can see from an example: for example, comments can belong to video or article. When there is a need to get video data from the comment table, polymorphic association is required.

A simple one sentence summary: one table corresponds to two tables.

1 realize polymorphic Association

1.1 structure of article table


  public function up()
  {
    Schema::create('articles', function (Blueprint $table) {
      $table->increments('id');
      $table->string('title');
      $table->text('body');$table->timestamps();
    });
  }

1.2 video table structure


  public function up()
  {
    Schema::create('videos', function (Blueprint $table) {
      $table->increments('id');
      $table->string('title');
      $table->text('description');
      $table->timestamps();
    });
  }

1.3 comment form structure


  public function up()
  {
    Schema::create('comments', function (Blueprint $table) {
      $table->increments('id');
      $table->text('content');
      $table->integer('item_id');
      $table->string('item_type');
      $table->timestamps();
    });
  }

↑ you need to specify Item here_ ID and item_ Type single introduction to item_ Type is mainly different from the table associated with it. Here, it has only two values: app \ article or app \ video.

1.4 writing polymorphic associations

Article and video:

public function comments()
  {
    /**
     *Second parameter: if your prefix is item_ Then write item. If it's something else, write something else.
     *The third parameter: item_ type
     *The fourth parameter: item_ id
     *The fifth parameter: the key associated with that table
     *(all but the second parameter above can be omitted)
     */
    return $this->morphMany(Comment::class, 'item', 'item_type', 'item_id', 'id');
  }

Comment：

public function video()
  {
    /**
     *All three parameters can be omitted, but K suggests you write them all
     */
    return $this->morphTo('item', 'item_type', 'item_id');
  }

use:


Route::get('/', function () {
  $video = App\Video::find(8);
  foreach ($video->comments as $comment) {
    echo $comment->id . ": " . $comment->item_type;
  }
});

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I hope this article will be helpful to your PHP Programming Based on laravel framework.