如何设置默认值 Laravel <select> 元素？

Question

我想检索类别名称中的数据库值，我想在选择中显示默认值。这是我的编辑视图控制器。

我有一个 category_product table.

<div class="col-md-4">
    <div class="form-group">
        <label for="category">category</label>
        <select class="form-control" name="category" id="category">
            @foreach($categories as $category)
                <option value="{{ $category->id }}" {{ $product->categories()->category_id == $category->id ? 'selected' : '' }}>{{ $category->name }}</option>
            @endforeach
        </select>
    </div>
</div>

ProductController.php

public function edit(Product $product)
{
    $categories = Category::all();
    return view('Admin.products.edit', compact('product', 'categories'));
}

Product.php

public function categories()
{
    return $this->belongsToMany(Category::class);
}

我收到这个错误。

Undefined property: Illuminate\Database\Eloquent\Relations\BelongsToMany::$category_id

Answer 1

您需要在 foreach() 循环上方的 select 标记中添加默认值。

<div class="col-md-4">
    <div class="form-group">
        <label for="category">category</label>
        <select class="form-control" name="category" id="category">
            <option value="xyz">xyz</option> /* set default option value */
            @foreach($categories as $category)
                <option value="{{ $category->id }}" {{$category->id == $category->id ? 'selected' : '' }}>{{ $category->name }}</option>
            @endforeach
        </select>
    </div>
</div>

如果要设置类别名称 selected 则需要匹配产品集合中的类别。（如果您在产品 table 中有 catetory_id ）

 <select class="form-control" name="category" id="category">

      @foreach($categories as $category)
           <option value="{{ $category->id }}" {{$product->catetory_id == $category->id ? 'selected' : '' }}>{{ $category->name }}</option>
      @endforeach
 </select>

如何设置默认值 Laravel <select> 元素？

How can I set the default value Laravel <select> element?

laravel-5.8