问题描述
我正在使用 LARAVEL 4 和 MySQL 后端.
I am using LARAVEL 4 with MySQL back-end.
我有一个 self-referencing 表，其中包含 id、name、type 和 parent 列.这里，parent 是Id 列的foreign-key.表中数据如下:
I have a self-referencing table with columns id, name, type and parent.
Here, parent is foreign-key of the column Id. The data in table is as below :
id name type parent
1 General group NULL
2 What is..? question 1
3 aa answer 2
4 bb answer 2
5 cc answer 2
6 How is..? question 1
7 ba answer 6
8 bb answer 6
9 Where is..? question 4
10 ca answer 9
11 cb answer 9
12 Who is..? question 6
13 da answer 12
14 db answer 12
15 Specific group NULL
16 When is..? question 15
17 ea answer 16
18 eb answer 16
19 Whome is..? question 2
20 fa answer 19
21 fb answer 19
22 fc answer 19
我想要一个使用此关系数据返回 nested JSON 的函数.例如:
I want a function that return nested JSON using this relational data. For example :
[{
"id" : 1,
"name" : "Geneal",
"type" : "group",
"children" : [{
"id" : 2,
"name" : "What is..?",
"type" : "question",
"children" : [{
"id" : 3,
"name" : "aa",
"type" : "answer"
},
{
"id" : 4,
"name" : "bb",
"type" : "answer"
},
{
"id" : 5,
"name" : "cc",
"type" : "answer"
}]},
{
"id" : 6,
"name" : "How is..?",
"type" : "question",
"children" : [{
"id" : 7,
"name" : "ba",
"type" : "answer"
},
{
"id" : 8,
"name" : "bb",
"type" : "answer"
}]
}]
... and so on
}]
我创建了一个名为 Survey 的 model，如下所示:
I have created a model named Survey as below :
class Survey extends BaseModel{
protected $table = 'questions';
protected $softDelete = false;
public function parent()
{
return $this->belongsTo('Survey', 'parent');
}
public function children()
{
return $this->hasMany('Survey', 'parent');
}
}
并在 controller 中调用它:
$user = Survey::all();
$parent = $user->parent()->first();
$children = $user->children()->get();
但我没有得到正确的结果，正如我在上面的 JSON 中提到的那样.
But I am not getting the proper result as I have mentioned in JSON above.
print_r($parent->toJson());
仅提供具有一级层次结构的记录(即组和问题，而不是答案).
gives records with one level hierarchy only (i.e group and questions, not answers).
同时
print_r($children ->toJson());
只提供问题(不提供组和答案).
Gives only questions (Not groups and answers).
我想要整个具有 N 层级的嵌套 JSON 格式的自引用数据.
我也试过了
$user = Survey::with('parent', 'children')->get();
但发现与上面的 $parent 相同.
But found same as $parent above.
有没有我可以得到想要的结果?
Is there anyway I can get the desired result?
提前谢谢..
推荐答案
以下是手动检索嵌套关系的方法:
Here's how you manually retrieve nested relations:
$collection = Model::with('relation1.relation2.relation3')->get();
所以你的情况是:
$surveys = Survey::with('children.children.children')->get();
显然，当关系固定时，这将完成这项工作，但这不是对同一张表建立递归关系的方法.
Obviously this will do the job when the relations are fixed, but it's not the way to go for a recursive relation to the same table.
幸运的是，你可以让这样的关系递归，那么你只需要检索整个树就是这样:
Fortunately, you can make such relation recursive, then all you need to retrieve whole tree is this:
$surveys = Survey::with('childrenRecursive');
但是，我不会以这种方式为每一行加载父级.
However, I wouldn't load parent for each row this way.
这就是你所需要的:
// Survey model
// loads only direct children - 1 level
public function children()
{
return $this->hasMany('Survey', 'parent');
}
// recursive, loads all descendants
public function childrenRecursive()
{
return $this->children()->with('childrenRecursive');
// which is equivalent to:
// return $this->hasMany('Survey', 'parent')->with('childrenRecursive);
}
// parent
public function parent()
{
return $this->belongsTo('Survey','parent');
}
// all ascendants
public function parentRecursive()
{
return $this->parent()->with('parentRecursive');
}
<小时>
要获得真正的树结构，第一个查询必须仅限于根节点:
To get real tree structure, first query must be limited to only root nodes:
$surveys = Survey::with('childrenRecursive')->whereNull('parent')->get();
这篇关于来自自引用表的 Laravel ORM 获取 N 级层次结构 JSON的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！