如何在编辑表单中未选择图像时默认使用当前图像更新帖子。我用的是laravel 8

// PostUpdateRequest.php

namespace App\Http\Requests;

use Illuminate\Foundation\Http\FormRequest;

class PostUpdateRequest extends FormRequest
{
    public function rules()
    {
        return [
            'title' => 'required',
            'content' => 'required',
            'image' => 'image|mimes:jpeg,png,jpg|max:2048',
        ];
    }
}

// PostController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use Illuminate\Support\Facades\Storage;
use App\Http\Requests\PostUpdateRequest;
use App\Models\Post;

class PostController extends Controller
{
    public function update(PostUpdateRequest $request, $id)
    {
        $post = Post::findOrFail($id);

        if ($request->hasFile('image')) {
            // 用户选择了图像文件
            $image = $request->file('image');
            $imagePath = $image->store('images', 'public');

            // 删除旧的图像文件
            Storage::disk('public')->delete($post->image);

            // 更新帖子的图像路径
            $post->image = $imagePath;
        }

        // 更新其他帖子字段
        $post->title = $request->input('title');
        $post->content = $request->input('content');
        $post->save();

        return redirect()->route('posts.show', $post->id);
    }
}