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Question

上下文

我有3次迁移：

成员表：

<?php   

class CreateMembersTable extends Migration
{    
    public function up()
    {
        Schema::create('members', function (Blueprint $table) {

             $table->increments('id');
             $table->string('name')->unique();
             $table->timestamps();
        });
    }    
}

成员链接类型表：

<?php

class CreateMemberLinkTypesTable extends Migration
{
    public function up()
    {
        Schema::create('member_link_types', function (Blueprint $table) {

            $table->string('name', 50)->primary()->unique();
            $table->string('category', 50)->index();
            $table->string('description', 50)->unique();
            $table->string('description_on_male', 50);
            $table->string('description_on_female', 50);
            $table->string('reverse_link', 50);
    });

    Artisan::call('db:seed', [
        '--class' => MemberLinkTypeSeeder::class
    ]);

    Schema::table('member_link_types', function ($table) {

        $table->foreign('reverse_link')->references('name')->on('member_link_types');
    });
}

并且，成员链接表：

<?php

class CreateMemberLinksTable extends Migration
{

    public function up()
    {
        Schema::create('member_links', function (Blueprint $table) {

            $table->increments('id');
            $table->string('member_link_type', 50)->index();
            $table->integer('from_member_id')->unsigned()->index();
            $table->integer('to_member_id')->unsigned()->index();
            $table->timestamps();
            $table->foreign('member_link_type')->references('name')->on('member_link_types');
            $table->foreign('from_member_id')->references('id')->on('members');
            $table->foreign('to_member_id')->references('id')->on('members');
        });
    }

}

在 seed member_link_types 表之后，它看起来像这样：

name   | category | description | description_on_male| description_on_female| reverse_link |
-------|----------|-------------|--------------------|----------------------|--------------|
child  | family   | Child       | son                | daughter             | parent |
parent | family   | Parent      | dad                | mon                  | child |
sibling| family   | Sibling     | brother            | sister               | sibling |
spouse | family   | Spouse      | husband            | wife                 | spouse |

因此，我在“成员链接类”模型中定义了关系：

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class MemberLink extends Model
{        

    protected $with = [
        'from', 'to', 'type'
    ];

    public function from()
    {
        return $this->belongsTo('App\Member', 'from_member_id');
    }

    public function to()
    {
        return $this->belongsTo('App\Member', 'to_member_id');
    }

    public function type()
    {
        return $this->belongsTo('App\MemberLinkType', 'member_link_type', 'name');
    }    

}

问题

鉴于我有这样的表“ member_links”：

| id | member_link_type | from_member_id | to_member_id |
|----|------------------|----------------|--------------|
| 1  | parent           |      1         |       2      |

当我加载模型时

$link = MemberLink::find(1)

我明白了：

App\MemberLink {#3012
     id: 1,
     member_link_type: "parent",
     from_member_id: 1,
     to_member_id: 2,
     from: App\Member {#3024
       id: 1,
       name: "Micaela Beltrão",       
     },
     to: App\Member {#3022
       id: 2,
       name: "Ian Fernandes",       
     },
     type: null,
   }

即，已成功加载 to 和 from 属性，但 type 关系没有成功（空）。

但是，如果我尝试直接从对象建立关系，则会得到不同的结果：

$link = MemberLink::find(1);
$link->belongsTo('App\MemberLinkType', 'member_link_type', 'name')->get()

为此：

=> Illuminate\Database\Eloquent\Collection {#3013
 all: [
   App\MemberLinkType {#3032
     name: "parent",
     category: "family",
     description: "Parent",
     description_on_male: "dad",
     description_on_female: "mom",
     reverse_link: "child",
   },
 ],

}

如何获取要加载的类型关系？

我正在使用Laravel 5.6。

更新1

在AarónGutiérrez建议之后，我添加了一个代理键（整数列）作为member_link_types表的键，并进行了必要的更改之后：

$link = MemberLink::find(1)
=> App\MemberLink {#3019
     id: 1,
     member_link_types_id: 1,
     from_member_id: 11,
     to_member_id: 12,
     created_at: "2018-08-14 14:28:46",
     updated_at: "2018-08-14 14:28:46",
     from: App\Member {#3031
       id: 11,
       name: "Simon Ferminiano",           
       created_at: "2018-08-14 14:24:49",
       updated_at: "2018-08-14 14:24:49",
     },
     to: App\Member {#3029
       id: 12,
       name: "Luciano Leon",

       created_at: "2018-08-14 14:24:52",
       updated_at: "2018-08-14 14:24:52",
     },
     type: App\MemberLinkType {#3030
       id: 1,
       name: "parent",
       category: "family",
       description: "Parent",
       description_on_male: "dad",
       description_on_female: "mom",
       reverse_link: 2,
     },

所以，我认为将文本字段用作表的主键时会受到一些限制吗？

Answer 1

在特定情况下，使用VARCHAR数据类型字段作为外键的目的是什么？

VARCHAR用于任何KEY的问题是它们可以保持白色空间。空白由任何非屏幕可读的内容组成字符，例如空格标签，回车符等。使用VARCHAR作为当您开始寻找原因时，一把钥匙会使您的生活变得困难表返回的记录末尾没有多余的空格键。

如此处所述：VARCHAR as foreign key/primary key in database good or bad?

所以，这可能是个问题。

Answer 2

默认情况下，只有模型关键点会出现在枢轴对象上。如果数据透视表包含额外的属性，则在定义关系时必须指定它们：

return $this->belongsTo('App\MemberLinkType')->withPivot('member_link_type');

来自https://laravel.com/docs/5.6/eloquent-relationships

编辑对不起，您尝试过吗？

$link->belongsTo('App\MemberLinkType', 'member_link_type', 'name')->with('type');

Answer 3

我能够解决。在$incrementing模型中，必须将false属性设置为MemberLinkType：

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class MemberLinkType extends Model
{
    public $timestamps = false;    
    public $incrementing = false;    
    protected $primaryKey = 'name';    

}

那之后，我得到了想要的东西：

$link = MemberLink::find(1)
=> App\MemberLink {#3071
     id: 1,
     member_link_type: "parent",
     from_member_id: 11,
     to_member_id: 12,
     created_at: "2018-08-14 15:03:22",
     updated_at: "2018-08-14 15:03:22",
     from: App\Member {#3065
       id: 11,
       name: "Gabriela Espinoza",           
     },
     to: App\Member {#3067
       id: 12,
       name: "Felipe Assunção",           
     },
     type: App\MemberLinkType {#3066
       name: "parent",
       category: "family",
       description: "Parent",
       description_on_male: "dad",
       description_on_female: "mom",
       reverse_link: "child",
     },
   }

关系不渴望加载

上下文

问题

更新1

3 个答案: