Laravel:在将列保存到数据库之前检查列的条件

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class AddConditionColumnToTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('your_table_name', function (Blueprint $table) {
            // 在将列保存到数据库之前检查列的条件
            if (Schema::hasColumn('your_table_name', 'your_column_name')) {
                $table->string('your_column_name')->nullable();
            }
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('your_table_name', function (Blueprint $table) {
            // 在回滚迁移时，可以撤销对列的修改
            if (Schema::hasColumn('your_table_name', 'your_column_name')) {
                $table->dropColumn('your_column_name');
            }
        });
    }
}