Laravel 5. 多对多关系。构建查询

Question

表格：

categories
--id

materials
--id

category_material
--id
--category_id
--material_id

型号：

class Material extends Model {
    public function categories(){
        return $this->belongsToMany('App\Category');
    }
}

class Category extends Model {
    public function materials(){
        return $this->belongsToMany('App\Material');
    }
}

我需要“category_id = 1”中的所有材料

尝试：

$category_id = '1';
$materials = Material::with('categories')->where('category_id', $category_id)->get();

未知列“materials.category_id”

$category_id = '1';
$materials = Material::with(['categories',function($query) use ($category_id){
    $query->where('category_id', $category_id);
}])->get();

Builder.php 第 792 行中的错误异常： explode() 期望参数 2 是字符串，给定对象

请帮帮我。

Answer 1

传递给with 的数组应为relation_name => closure 格式

$category_id = '1';
$materials = Material::whereHas('categories', function($query) use ($category_id){
    $query->where('category_id', $category_id);
})->get();