Laravel 通过模型关系

Question

我有 3 个表的顺序如下：

1. it has -> id学校it has -> id
2. it has -> school_id
3. SemesterClass it has -> semester_id

现在我试图在School和SemesterClass之间建立关系，以获得每所学校的班级列表以及每班学校的名称。

根据文档，我有这种关系：

学校模式

class School extends Model
{
    public function semesters() {
        return $this->hasMany(SchoolSemester::class);
    }

    public function classes() {
        return $this->hasManyThrough(SemesterClass::class, SchoolSemester::class);
    }
}

学校学期模式

class SchoolSemester extends Model
{
    public function school() {
        return $this->belongsTo(School::class);
    }

    public function classes() {
        return $this->hasMany(SemesterClass::class, 'semester_id', 'id');
    }
}

学期班模式

class SemesterClass extends Model
{
    public function school() {
        return $this->hasOneThrough(School::class, SchoolSemester::class, 'school_id', 'id');
    }

    public function semester() {
        return $this->belongsTo(SchoolSemester::class, 'semester_id', 'id');
    }
}

控制器

public function show($id)
{
    $class = SemesterClass::with(['school', 'teacher', 'teacher.user', 'students'])->findOrFail($id);
    dd($class);
    //return view('admin.Classes.show', compact('class'));
}

结果

任何的想法？

Answer 1

您的中间表是school_semester ，laravel会发现foreign_key school_semester_id默认情况下，但是，您的foreign_key是semester_id ，所以你需要指定在foreign_key hasManyThrough ：

    public function classes() {
        return $this->hasManyThrough(
            SemesterClass::class, 
            SchoolSemester::class
            'school_id', // Foreign key on school_semesters table...
            'semester_id', // Foreign key on classes table...
            'id', // Local key on schools table...
            'id' // Local key on school_semesters table...
        );
     }

并像这样更改您的hasOneThrough代码：

 public function school() {
        return $this->hasOneThrough(
             School::class, 
             SchoolSemester::class, 
             'id',
             'id',
             'semester_id',
             'school_id' );
    }

另一个解决方案：

因为反向只是两个 BelongsTo 关系的串联，所以您可以将belongsTo放在belongsTo和 School Model 中。 并得到这样的关系：

SemesterClass::with(['semester.school'])

或者你可以在 SemesterClass 模型中定义一个 mutator：

protected $appends = ['school'];

public function getSchoolAttribute() {
    return $this->semester->school;
}