雄辩的关系和多维集合拒绝

Question

I have a school database which hasMany teacher, and which hasMany student like this:

class School extends Model
{
    public function teachers()
    {
        return $this->hasMany(Teacher::class,'school_id');
    }
}

class Teacher extends Model
{
    public function students()
    {
        return $this->hasMany(Student::class,'teacher_id');
    }
}

class Student extends Model
{
}

---

The full query

$full = School::with(['teachers' => function ($query) {
    $query->with('students');
}])->get();

And the result is like this:

[
    {
        "id": 1,
        "school_name": "First Park",
        "teachers": [
            {
                "id": 1,
                "teacher_name": "Mr.Aha",
                "students": [
                    {
                        "id": 1,
                        "student_name": "Jane",
                        "drop": 1
                    },
                    {
                        "id": 2,
                        "student_name": "Jon",
                        "drop": 0
                    }
                ]
            }
        ]
    }
]

---

Now I want to remove student who drop school and select teacher_name, so I try to do it with eloquent and collection, but they all fail.

The eloquent way is:

School::with(['teachers' => function ($teacher) {
    $teacher->with(['students' => function ($student) {
        $student->where('drop', '!=', 0)
    }])->select('teacher_name');
}])->get();

But the result output, teacher is an empty object.

---

The collection way is base on the full query

$full->map(function ($teacher) {
    unset($teacher->id);//there are more column to unset in real life
    $teacher->reject(function ($student) {
        return $student->drop == 0;
    });
});

But the result is the same as full query.

---

I don't know which way is better, eloquent or collection, but they won't work

Answer 1

You also have to select the id and school_id columns that are required for eager loading:

School::with(['teachers' => function ($teacher) {
    $teacher->with(['students' => function ($student) {
        $student->where('drop', '!=', 0)
    }])->select('id', 'school_id', 'teacher_name');
}])->get();

Then remove them afterwards or use $hidden :

$full->map(function ($teacher) {
    unset($teacher->id, $teacher->school_id);
});

Answer 2

Example from original docs.

Nested Eager Loading To eager load nested relationships, you may use "dot" syntax. For example, let's eager load all of the book's authors and all of the author's personal contacts in one Eloquent statement:

$books = App\\Book::with('author.contacts')->get();

also, you can use load() method