如何防止用户从数据库中删除某一行,如果有什么东西引用了它

wz8daaqr  于 2021-10-10  发布在  Java
关注(0)|答案(0)|浏览(157)

我正在开发一个 Jmeter 板,用户可以创建互联网提供商,然后他可以将数据包与之关联。问题是,如果用户在关联的internet提供商之后删除,当我转到数据包时,网页会崩溃,因为它试图访问不存在的internet提供商。因此,我想防止如果在另一个表中引用internet提供商1次或多次,则用户无法删除它。
internet提供商删除功能:

public function destroy(Internet $provider)
{
    $oldName = $provider->name;
    $oldUrlFoto = $provider->image_url;
    try {

        Storage::delete('public/provider/' . $oldUrlFoto);
        $provider->delete();
        return redirect()->route('admin.providers')
            ->with('alert-msg', 'The provider "' . $provider->name . '" was deleted!')
            ->with('alert-type', 'success');
    } catch (\Throwable $th) {
        // $th é a exceção lançada pelo sistema - por norma, erro ocorre no servidor BD MySQL
        // Descomentar a próxima linha para verificar qual a informação que a exceção tem

        if ($th->errorInfo[1] == 1451) {   // 1451 - MySQL Error number for "Cannot delete or update a parent row: a foreign key constraint fails (%s)"
            return redirect()->route('admin.providers')
                ->with('alert-msg', 'We cant delete this provider "' . $oldName . '", because its already in use!')
                ->with('alert-type', 'danger');
        } else {
            return redirect()->route('admin.providers')
                ->with('alert-msg', 'We cant delete this provider "' . $oldName . '". Error: ' . $th->errorInfo[2])
                ->with('alert-type', 'danger');
        }
    }
}

数据包模型和互联网提供商模型:

class Packets extends Model
{
    use HasFactory, SoftDeletes;

    protected $fillable = ['internet_provider_id', 'name', 'price'];

    public function internetProvider()
    {
        return $this->belongsTo(Internet::class, 'internet_provider_id');
    }
}

class Internet extends Model
{
    use HasFactory, SoftDeletes;

    protected $fillable = ['name', 'image_url'];

    public function packets()
    {
        return $this->hasMany(Packets::class);
    }
}

迁移:

Schema::create('internet', function (Blueprint $table) {

    $table->bigInteger('id')->unsigned()->autoIncrement();
    $table->string('name', 50);
    $table->string('image_url');

    $table->timestamps();
    // Clientes podem ser apagados com "soft deletes"
    $table->softDeletes();
});

Schema::create('packets', function (Blueprint $table) {
    $table->bigInteger('id')->unsigned()->autoIncrement();
    $table->bigInteger('internet_provider_id')->unsigned();
    $table->foreign('internet_provider_id')->references('id')->on('providers');
    $table->string('name');
    $table->string('price');

    $table->timestamps();
    $table->softDeletes();
});

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