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php - Laravel belongsTo 和 hasMany 不返回数据

问题描述

我是 laravel/eloquent 的新手，到目前为止非常喜欢它们，但我无法让 belongsTo 和 hasMany 工作。我已经阅读了其他人遇到的无数问题，但还没有找到可以为我解决问题的解决方案。

我有一个“页面”模型和一个“类别”模型。这是表的定义：

Schema::create('pages', function (Blueprint $table) {
    $table->increments('id');
    $table->string('name');
    $table->timestamps();
});

Schema::create('categories', function (Blueprint $table) {
    $table->increments('id');
    $table->integer('page_id');
    $table->foreign('page_id')->references('id')->on('pages');
    $table->string('name');
    $table->timestamps();
});

这是我的页面模型：

namespace App;

use Illuminate\Database\Eloquent\Model;

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

这是我的类别模型：

namespace App;

use Illuminate\Database\Eloquent\Model;

class Category extends Model
{
    public function page() 
    {
        return $this->belongsTo('App\Page');
    }
}

以下是一些修补的结果：

> php artisan cache:clear
Application cache cleared!
> php artisan tinker
>>> \App\Category::find(1)
=> App\Category {#2916
     id: "1",
     page_id: "1",
     name: "First Category",
     created_at: "2018-12-30 03:18:07.347",
     updated_at: "2018-12-30 03:18:07.347",
   }
>>> \App\Category::find(1)->page()
=> Illuminate\Database\Eloquent\Relations\BelongsTo {#2918}
>>> \App\Page::find(1)
=> App\Page {#2902
     id: "1",
     name: "First Page",
     created_at: "2018-12-30 03:18:07.220",
     updated_at: "2018-12-30 03:18:07.220",
   }
>>> \App\Page::find(1)->categories()
=> Illuminate\Database\Eloquent\Relations\HasMany {#2922}
>>>

我得到我的对象就好了，但是当我尝试拉关系时，我只是得到看起来像空对象的东西：

=> Illuminate\Database\Eloquent\Relations\BelongsTo {#2918}

=> Illuminate\Database\Eloquent\Relations\HasMany {#2922}

如果我将我的 page() 和 categories() 函数换成这样的函数，一切都很好：

public function page() 
{
    return \App\Page::find($this->page_id);
}

public function categories()
{
    return \App\Category::where('page_id', $this->id)->get();
}

以下是这些结果：

> php artisan cache:clear
Application cache cleared!
> php artisan tinker
Psy Shell v0.9.9 (PHP 7.3.0 — cli) by Justin Hileman
>>> \App\Page::find(1)
=> App\Page {#2916
     id: "1",
     name: "First Page",
     created_at: "2018-12-30 03:18:07.220",
     updated_at: "2018-12-30 03:18:07.220",
   }
>>> \App\Page::find(1)->categories()
=> Illuminate\Database\Eloquent\Collection {#2918
     all: [
       App\Category {#2921
         id: "1",
         page_id: "1",
         name: "First Category",
         created_at: "2018-12-30 03:18:07.347",
         updated_at: "2018-12-30 03:18:07.347",
       },
       App\Category {#2922
         id: "2",
         page_id: "1",
         name: "Second Category",
         created_at: "2018-12-30 03:18:07.480",
         updated_at: "2018-12-30 03:18:07.480",
       },
       App\Category {#2923
         id: "3",
         page_id: "1",
         name: "Third Category",
         created_at: "2018-12-30 03:18:07.623",
         updated_at: "2018-12-30 03:18:07.623",
       },
     ],
   }
>>> \App\Category::find(1)
=> App\Category {#2904
     id: "1",
     page_id: "1",
     name: "First Category",
     created_at: "2018-12-30 03:18:07.347",
     updated_at: "2018-12-30 03:18:07.347",
   }
>>> \App\Category::find(1)->page()
=> App\Page {#2921
     id: "1",
     name: "First Page",
     created_at: "2018-12-30 03:18:07.220",
     updated_at: "2018-12-30 03:18:07.220",
   }
>>>

编辑：

我发现如果我添加->get()我会在修补时看到数据，正如我所期望的那样：

public function page() 
{
    return $this->belongsTo('App\Page')->get();
}

然而，我见过的例子都没有显示有人这样做。我只是误解了这应该如何工作吗？我希望在修补时只做 $page->categories(); 会给我类别而不需要做 $page->categories()->get();

标签： phplaravellaravel-5.7

解决方案

试试这个。

    Schema::create('categories', function (Blueprint $table) {
    $table->increments('id');
    $table->integer('page_id')->unsigned();
    $table->foreign('page_id')->references('id')->on('pages');
    $table->string('name');
    $table->timestamps();
});

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