when you use first() function at the end of your code, its return a single row and that is the first row. when using get() function at the end of your code, its return a set of rows that are in your Query. when you use find() and its return value is null, you cant call where() after that!
I think you must write your controller like this:
public function productCategory($id)
{
$product_category=product_category::find($id);
return view('product_category', compact('product_category'));
}
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评论（1）
这个语法是不正确的！
阅读此文档以获取（）：
https://laravel.com/docs/docs/9.x/eloquent#检索单个模式
阅读此文档有关（）：
<条款
我的描述：
当您想找到一个product_category行时，必须编写此（例如，使用ID 7的product_category）：
或
当您使用时
first（）函数在代码末尾，它返回一行，这是第一行。在代码末尾使用get（）函数时，它返回查询中的一组行。当您使用
find（）且其返回值为null时，您无法调用where（）之后！我认为您必须这样写您的控制器：
我建议您读过有关Laravel的雄辩：
https://laravel.com/docs/9.x/eloquent
以及关于Laravel查询构建器：
https://laravel.com/docs/9.x/ceries
this syntax is not correct!
read this document for find():
https://laravel.com/docs/9.x/eloquent#retrieving-single-models
read this document for where():
https://laravel.com/docs/9.x/queries#where-clauses
my description:
when you want to find a single product_category row you must write this (for example product_category with id 7):
or
when you use
first()function at the end of your code, its return a single row and that is the first row. when usingget()function at the end of your code, its return a set of rows that are in your Query.when you use
find()and its return value is null, you cant callwhere()after that!I think you must write your controller like this:
I suggest you read about Laravel Eloquent much:
https://laravel.com/docs/9.x/eloquent
and about Laravel Query builder:
https://laravel.com/docs/9.x/queries