get many to many values and which of them are selected in laravel - laravel

Question

Contacts:
id
name
Tags:
id
name
ContactTags:
contact_id
tag_id
In Contacts model:
public function tags()
{
return $this->belongsToMany(Tags::class, "contacts_tags", "contact_id", "tag_id");
}
So if I do
$contact = Contacts::findOrFail($id);
dd($contact->tags);
I successfully get the tags associated with the contact. But how can I get all tags and a flag indicating which one of those is associated?
I'm trying to prevent fetching all tags, loop them and with each iteration loop all contact_tags and check if tag_id matches. I want to display a list of checkboxes with all tags and check the ones that are in the relation.

Answer 1

This code can help you, but I'm using the SELECT multiple component. You can easily adapt it to use the CHECKBOX component.
Contacts model:
public function tags()
{
return $this->belongsToMany(Tags::class, "contacts_tags", "contact_id", "tag_id");
}
ContactController.php
public function edit(Contact $contact)
{
$tags = Tag::all();
return view('contacts.edit',compact('contact', 'tags'));
}
edit.blade.php
<div class="row">
<div class="col">
<div class="form-group">
<strong>Tags:</strong>
<select name="tags_id[]" multiple>
#foreach ($tags as $tag)
#if( $contact->tags->contains($tag) )
<option value="{{ $tag->id }}" selected>{{ $tag->name }}</option>
#else
<option value="{{ $tag->id }}">{{ $tag->name }}</option>
#endif
#endforeach
</select>
</div>
</div>
</div>
Update in ContactController.php
public function update(Request $request, Post $contact)
{
$validatedData = $request->validate([
'tags_id' => ['array'],
]);
$contact->update($request->all());
$contact->tags()->sync($validatedData['tags_id']);
return redirect()->route('contact.index')->with('success', 'Contact successfully updated!');
}
The validation is just an example. The $validatedData has no use here, but it can be used to update the contact if you validate the other fields.