Laravel Eloquent ORM - Many to Many Delete Pivot Table Values left over

问题

Using Laravel, I have the following code

$review = Review::find(1);
$review->delete();

Review has a many to many relationship defined with a Product entity. When I delete a review, I'd expect it to be detached from the associated products in the pivot table, but this isn't the case. When I run the code above, I still see the linking row in the pivot table.

Have I missed something out here or is this the way Laravel works? I'm aware of the detach() method, but I thought that deleting an entity would also detach it from any related entities automatically.

Review is defined like this:

<?php
class Review extends Eloquent
{
    public function products()
    {
        return $this->belongsToMany('Product');
    }
}

Product is defined like this:

<?php
class Product extends Eloquent
{
    public function reviews()
    {
        return $this->belongsToMany('Review');
    }
}

Thanks in advance.

回答1:

The detach method is used to release a relationship from the pivot table, whilst delete will delete the model record itself i.e. the record in the reviews table. My understanding is that delete won't trigger the detach implicitly. You can use model events to trigger a cleanup of the pivot table, though, using something like:

Review::deleting(function($review)
{
    $review->product()->detach()
}

Also, I would suggest that the relationship would be a one to many, as one product would have many reviews, but one review wouldn't belong to many products (usually).

class Review extends \Eloquent {
    public function product()
    {
        return $this->belongsTo('Product');
    }
}

class Product extends \Eloquent {
    public function reviews()
    {
        return $this->hasMany('Review');
    }
}

Of course, this would then require that you tweak your database structure. If you wanted to leave the database structure and your current relationships as they are, the other option would be to apply a foreign key constraint on the pivot table, such that when either a review or product is removed, you could cascade the delete on the pivot table.

// Part of a database migration
$table->foreign('product_id')->references('id')->on('products')->onDelete('cascade');
$table->foreign('review_id')->references('id')->on('reviews')->onDelete('cascade');

Edit: In adding the constraint, you push the cleanup work onto the database, and don't have to worry about handling it in code.

回答2:

Simpler Steps:

In this example an Account has many Tags:

To delete the Tags, then the Account do this:

// delete the relationships with Tags (Pivot table) first.
$account->find($this->accountId)->tags()->detach();

// delete the record from the account table.
$account->delete($this->accountId);

On the Pivot Table make sure you have ->onDelete('cascade');

$table->integer('account_id')->unsigned()->index();
$table->foreign('account_id')->references('id')->on('accounts')->onDelete('cascade');

$table->integer('tag_id')->unsigned()->index();
$table->foreign('tag_id')->references('id')->on('tags')->onDelete('cascade');

回答3:

$review->product()->sync([]) also works.

However $review->product()->detach() is much more explicit.

来源：https://stackoverflow.com/questions/27330551/laravel-eloquent-orm-many-to-many-delete-pivot-table-values-left-over

标签

laravel

orm

many-to-many

eloquent