Laravel 4 和 Eloquent：检索所有记录和所有相关记录

Laravel 4 and Eloquent: retrieving all records and all related records

提问by tptcat

I have two classes: Artistand Instrument. Each Artistcan play one or more Instruments. And each Instrumentcan be assigned to one or more Artists. So, I've set up the following Classes:

我有两个类：Artist和Instrument。每个人Artist可以玩一个或多个Instrument。并且每个Instrument都可以分配给一个或多个Artists。所以，我设置了以下类：

Artist.php

艺术家.php

public function instruments() {
    return $this->belongsToMany('App\Models\Instrument');
}

Instrument.php

仪器.php

public function artists() {
    return $this->belongsToMany('\App\Models\Artist');
}

Then I have three database tables:

然后我有三个数据库表：

artists: id, firstname, lastname, (timestamps)
instruments: id, name
artist_instrument: id, artist_id, instrument_id

I'm able to successfully retrieve a oneartist and their associated instruments like so:

我能够成功检索一位艺术家及其相关乐器，如下所示：

ArtistController.php

艺术家控制器.php

$artist = Artist::find($artist_id);
$instruments = $artist->instruments()->get();
return \View::make('artists')->with('artists', $artists)->with('instruments', $instruments);

I have 3 questions:

我有3个问题：

1. In my view, I can output the $artistlike:

   {{ $artist->firstname }}
   

   and I can iterate through $instrumentslike:

   @foreach ($instruments as $instrument)
       <h2>{{ $instrument->name }}</h2>
   @endforeach
   

   but is it possible to iterate over $artist(I know there's only one —?see #2) and for each $artistiterate over their $instruments?

2. In my controller, how would I get allartists and for each of those their associated instruments with the end goal of iterating through them in my view as described in #1.

3. Is it possible to only retrieve specific columns in the above example of ArtistController.php? I've tried this:

   $artist = Artist::where('id', $artist_id)->get('firstname');
   $instruments = $artist->instruments()->get();
   return \View::make('artists')->with('artists', $artists)->with('instruments', $instruments);
   

   but I get an error saying Collection::instruments()is undefined.

1. 在我看来，我可以输出$artist如下：

   {{ $artist->firstname }}
   

   我可以$instruments像这样迭代：

   @foreach ($instruments as $instrument)
       <h2>{{ $instrument->name }}</h2>
   @endforeach
   

   但是是否可以迭代$artist（我知道只有一个 - ？见#2）并且每次$artist迭代它们$instruments？

2. 在我的控制器中，我将如何获得所有艺术家以及每个艺术家的相关乐器，最终目标是在我的视图中迭代它们，如#1 中所述。

3. 是否可以仅检索上述示例中的特定列ArtistController.php？我试过这个：

   $artist = Artist::where('id', $artist_id)->get('firstname');
   $instruments = $artist->instruments()->get();
   return \View::make('artists')->with('artists', $artists)->with('instruments', $instruments);
   

   但我收到一条错误消息，说Collection::instruments()未定义。

I'm assuming there's something not right in my model relationships. I've also tried defining my relationship in Artist.phpwith a hasMany(I think it makes more sense to say "Each Artist hasMany Instruments", but that gives me an error because it's expecting a table named artists_instrumentsand it's also trying to retrieve columns that wouldn't exists in that table (like name).

我假设我的模型关系中有些不对劲。我也试着定义我的关系Artist.php与hasMany（我认为它更有意义，说：“每一位艺术家的hasMany仪器”，但给我一个错误，因为它是期待一个表命名artists_instruments，它也试图找回那列该表中不存在（如name）。

回答by Joseph Silber

Your model relationships are fine.

你的模型关系很好。

Controller:

控制器：

$artists = Artist::with('instruments')->get();

return \View::make('artists')->withArtists($artists);

View:

看法：

@foreach ($artists as $artist)

    <h1>{{ $artist->firstname }}</h1>

    @foreach ($artist->instruments as $instrument)

        <h2>{{ $instrument->name }}</h2>

    @endforeach

@endforeach