[英]Relationship to a third model through a pivot table in Laravel
我是 Laravel 的初學者,我正在使用以下模式:
Course {
id,
name,
teacher_id
}
Category {
id,
name
}
Teacher {
id,
name
}
CategoryCourses {
id,
course_id,
category_id
}
如您所見,CategoryCourses 是我的數據透視表,我在 Courses 和 Category 之間使用belongsToMany
。
現在——我想做什么? 我正在嘗試為類別創建一個show
視圖,在其中單擊類別,它應該顯示具有該類別的所有課程以及教授該課程的教師。
例如 - 如果我有 4 門 Laravel 課程,其中包含“Web 開發”類別 - 我想將所有課程顯示在一張卡片上,並在每個課程中顯示老師的姓名。
以下是我的模型:
類別
class Category extends Model
{
use HasFactory;
protected $fillable = [
'name'
];
public function courses()
{
return $this->belongsToMany(Course::class, 'course_categories', 'course_id', 'category_id');
}
public function teacher()
{
return $this->hasOneThrough(Teacher::class, CourseCategory::class);
}
}
課程:
class Course extends Model
{
use HasFactory;
protected $fillable = [
'name','description','cover','difficulty', 'teacher_id'
];
public function teachers() {
return $this->belongsTo(Teacher::class, 'teacher_id', 'id');
}
public function categories() {
return $this->belongsToMany(Category::class, 'course_categories');
}
}
老師:
class Teacher extends Authenticatable
{
use HasFactory;
protected $fillable = [
'name','email','password', 'avatar'
];
public function courses() {
return $this->hasMany('Course', 'teacher_id');
}
}
類別控制器 - 顯示($id) :
public function show($id)
{
$category = Category::findOrFail($id)->first();
$course = Category::with('courses','teacher')->get();
return view('admin.showcoursesbycategory', compact('category', 'course'));
}
這是我在編寫$course = Category::with('teacher')
代碼后遇到的錯誤:
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'teachers.course_category_id' in 'on clause' (SQL: select `teachers`.*, `course_categories`.`category_id` as `laravel_through_key` from `teachers` inner join `course_categories` on `course_categories`.`id` = `teachers`.`course_category_id` where `course_categories`.`category_id` in (1, 2, 3, 4))
我如何實現我想要做的事情? 我究竟做錯了什么? 請在這里幫助我。
假設每門課程只有一位老師,按照正常的命名約定,關系應該在Course
模型上命名為teacher
class Course extends Model
{
use HasFactory;
protected $fillable = [
'name','description','cover','difficulty', 'teacher_id'
];
public function teacher() {
return $this->belongsTo(Teacher::class, 'teacher_id', 'id');
}
public function categories() {
return $this->belongsToMany(Category::class, 'course_categories', 'course_id', 'category_id');
}
}
我想您需要修復Category模型中的關系簽名
class Category extends Model
{
use HasFactory;
protected $fillable = [
'name'
];
public function courses()
{
/**
* Change
* return $this->belongsToMany(Course::class, 'course_categories', 'course_id', 'category_id');
*/
return $this->belongsToMany(Course::class, 'course_categories', 'category_id', 'course_id');
}
public function teacher()
{
return $this->hasOneThrough(Teacher::class, CourseCategory::class);
}
}
然后在控制器中,您可以將查詢編寫為
public function show($id)
{
$category = Category::with('courses.teacher')->findOrFail($id);
return view('admin.showcoursesbycategory', compact('category'));
}
然后在視圖中你可以
<h1>{{ $category->name }}</h1>
<p>======== Courses ========</p>
@foreach($category->courses as $course)
<p>{{ $course->name }}</p>
<p>Conducted By: {{ $course->teacher->name }}</p>
@endforeach
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