属于Parent模型的三个模型的Laravel 8关系

Question

大家好，我目前正在从事一个 laravel 项目，我有一个父表，其中有三个表的 id 引用它。这些表迁移也有各自的模型。以下是表迁移文件：

create_products_table.php

        Schema::create('products', function (Blueprint $table) {
            $table->id();
            $table->string('product_id', 10);
            $table->string('product_name');
            $table->string('image');
            $table->string('images');
            $table->string('product_description');
            $table->bigInteger('size_id')->unsigned();
            $table->string('color');
            $table->string('product_quantity');
            $table->string('old_price');
            $table->string('discount');
            $table->string('product_price');
            $table->bigInteger('user_id')->unsigned()->nullable();
            $table->bigInteger('category_id')->unsigned();
            $table->bigInteger('gender_id')->unsigned();
            $table->timestamps();
            $table->foreign('size_id')->references('id')->on('sizes')->onDelete('cascade');
            $table->foreign('category_id')->references('id')->on('categories')->onDelete('cascade');
            $table->foreign('gender_id')->references('id')->on('genders')->onDelete('cascade');
        });

create_genders_table.php

        Schema::create('genders', function (Blueprint $table) {
            $table->id();
            $table->string('gender_class');
            $table->timestamps();
        });

create_categories_table.php

        Schema::create('categories', function (Blueprint $table) {
            $table->id();
            $table->string('cat_name');
            $table->timestamps();
        });

create_sizes_table.php

        Schema::create('sizes', function (Blueprint $table) {
            $table->id();
            $table->string('sizes');
            $table->timestamps();
        });

这也是我分别在他们的模型上定义关系的方式

产品.php

    public function category()
    {
        return $this->belongsTo(Category::class);
    }
    
    public function gender()
    {
        return $this->belongsTo(Gender::class);
    }
    
    public function size()
    {
        return $this->belongsTo(Size::class);
    }

Category.php

    public function products()
    {
        return $this->hasMany(Product::class);
    }

性别.php

    public function products()
    {
        return $this->hasMany(Product::class);
    }

大小.php

    public function products()
    {
        return $this->hasMany(Product::class);
    }

我实际上是一个 laravel 初学者，我在 laravel.com 研究了雄辩的模型关系，所以我所做的只是基于我对一对多关系的理解。当我用 dd($request) 检查我的所有请求时，category_id、gender_id、size_id 都显示为 null，我相信这是因为我没有正确定义关系。现在，我非常需要您的帮助。

请各位经验丰富的开发人员帮忙，我非常需要您的帮助，如果今天能收到您的回复，我将不胜感激。提前致谢。

Answer 1

=>Everything is right, just make changes in the products migration add this code.

$table->foreign('size_id')->references('id')->on('products')->onDelete('cascade');
            $table->foreign('category_id')->references('id')->on('products')->onDelete('cascade');
            $table->foreign('gender_id')->references('id')->on('products')->onDelete('cascade');

=>and migrate table