Can't modifiy eloquent query result - laravel

Question

So I got the following code in my controller's show function which just returns a page with the tags:
$page = Post::with('tags')->findOrFail($id);
$page->tags->lists('name');
return response($page);
When I try to to execute this, it won't change the tags key, which is an array with the tags from the eloquent belongsToMany relationship.
Why isn't this working? To me it seems pretty handy to just change a value like this.
When I change it to $page->test = $page->tags->lists('name') it will add the test key as usual.
How would I modify a eloquent value in a easy way?

Answer 1

What works pretty well for such cases is overriding toArray in your Model:
public function toArray(){
$array = parent::toArray();
$array['tags'] = $this->tags->lists('name');
return $array;
}

Answer 2

After the $page = Post::with('tags')->findOrFail($id); line is executed, $page->tags is going to be an Illuminate\Database\Eloquent\Collection object containing all the related Tags for the Post. From your provided code and question, it sounds like you want to then change $page->tags to be an array containing just the related tag names.
The statement $page->tags->lists('name') is only going to return an array of all the names of the related tags; it does not modify the underlying collection. If you wanted to modify the $page->tags attribute, you would need to assign it the result of your statement:
$page->tags = $page->tags->lists('name');
However, $page->tags was an attribute that was dynamically created and assigned by the Model, and is expected to hold the contents of a relationship. Manually modifying the contents like this may have unintended consequences, but I do not know.
Edit
The Model::toArray() method merges in the relationship information over the attribute information. So, you can change the attribute, but if you echo the model, the relationship information will show up over your attribute change.
$page->tags = $page->tags->lists('name');
// this will echo the tags attribute, which is now the array of tags
echo print_r($page->tags, true);
// this will echo the model, with the tags attribute being
// overwritten with the related data
echo $page;
One option would be to unset the attribute (which also unsets the relationship) and then reassign the attribute to your desired data:
$page = Post::with('tags')->findOrFail($id);
$temp = $page->tags;
unset($page->tags); // you must unset the attribute before reassigning it
$page->tags = $temp->lists('name');
return response($page);
A little bit cleaner would be to use a different attribute name:
$page = Post::with('tags')->findOrFail($id);
$page->tagNames = $page->tags->lists('name');
unset($page->tags);
return response($page);
And another option is to do what #lukasgeiter suggested and override the Model::toArray method:
class Post extends Model {
public function toArray() {
// call the parent functionality first
$array = parent::toArray();
if (isset($this->tags)) {
$array['tags'] = $this->tags->lists('name');
}
return $array;
}
}

Answer 3

If you want to change the output of one of the relationships in the toArray/toJson methods, then use accessor:
// in order to not show the underlying collection:
protected $hidden = ['tags'];
// in order to append accessor to toArray output
protected $appends = ['allTags'];
// mutate the collection to be just an array of tag names
public function getAllTagsAttribute()
{
$collection = return $this->getRelation('tags');
return ($relation) ? $collection->lists('name') : [];
}
then you will get simple array instead of collection when you do $page->allTags or in the toArray/toJson output, while not showing the real collection.
It is allTags not `tags, since the latter should remain eloquent dynamic property, so you can work with it as usual before outputting anything.

Answer 4

not sure if this helps. To be honest, I do not get your point. But I guess there is something wrong with this line:
$page->tags->lists('name');
If $page->tags is a belongsToMany relationship and you want to add more query conditions after this relationship, you should query like this:
$page->tags()->lists('name');