在laravel中组合查询结果

Question

On my website, users can upload images and attach tags to those images.

I've got an images table,a tag table and an images_tag pivot table.

Images can have many tags, and tags can belong to many images.

I want to be able to generate a list of all the tags a user has used in his/her images.

$imageIDs = Images::where('created_by', Auth::user()->id)->lists('id');

So this would create a list of all the image IDs that a user has upload.

What I want is essentially "foreach $imageIDs, check the images_tag table and for every match go to the tags table and get me back the tagname value."

But I have no idea how I'd do that.

Maybe a foreach then use the merge method on all the results? Any help would be appreciated!

Answer 1

What you could do is this.

class Tag extends Model
{
    public function images()
    {
        return $this->belongsToMany(Image::class);
    }
}

class SomeController
{
    public function someMethod()
    {
        $tags = Tag::with(['images' => function ($image) {
            return $image->where('created_by', Auth::user()->id);
        }])->select('id', 'tagname')->get();
        // these are your $tags 
    }
}

You should not use a query inside foreach() . Then it would result N+1 problem . What you instead do is eager loading using with() statement.

Answer 2

You need to use whereHas() to check the relationship:

$userTags = Tags::whereHas('images', function($q) {
    $q->where('created_by', auth()->user()->id);
})->get();

Then just pass this data to a view:

return view('some.view', compact('userTags'));

And iterate over tags in a view:

@foreach ($userTags as $tag)
    {{ $tag->name }}
@endforeach