Displaying a category when editing a post in laravel - php

Question

I am creating a blog in Laravel. I have two tables - posts and categories.
When i want to edit one post, i have a problem with categories. My post controller is sending categories to the view, i can see them while editing, but i don't know how to set the current category in the select option.
The tables are conected:
public function posts(){
return $this->hasMany('App\Post');
}
public function category(){
return $this->belongsTo('App\Category');
}
Controller:
public function edit(Post $post)
{
$categories = Category::all();
return view('admin.posts.edit', compact('post'))->withCategories($categories);
}
View:
<form action="{{ route('posts.update', ["post" => $post->id]) }}" method="post" enctype="multipart/form-data" class="form-horizontal">
#csrf
<div class="form-body">
<div class="form-group">
<label class="col-md-3 control-label">Naslov</label>
<div class="col-md-4">
<input type="text" name='title' value='{{ old("title", $post->title) }}' class="form-control">
#if($errors->has('title'))
<div class='text text-danger'>
{{ $errors->first('title') }}
</div>
#endif
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Kategorija</label>
<div class="col-md-4">
<select class="form-control" name="category_id">
#if(count($categories) > 0)
#foreach($categories as $category)
<option value="{{ $category->id }}">{{ $category->name }}</option>
#endforeach
#endif
</select>
#if($errors->has('category_id'))
<div class='text text-danger'>
{{ $errors->first('category_id') }}
</div>
#endif
</div>
</div>
How can i make the category display the current category of the selected post in the option select like i have for title? value='{{ old("title", $post->title) }}'

Answer 1

To show the currently associated Category, you can set a default "selected" option based on the $post->category_id:
<option value="{{ $category->id }}" {{ old('category_id', $post->category_id) == $category->id ? 'selected' : '' }}>{{ $category->name }}</option>
This a simple ternary that sets the selected attribute of one of the options based on the old() value, or, if old() is not set, then based on the value of $post->category_id

Answer 2

What you are looking for is the selected property of the <option> element.
#forelse ($categories as $category)
<option value="{{ $category->id }}" {{ $category->id == old('category_id', $post->category_id) ? 'selected' : '' }}>
{{ $category->name }}
</option>
#endforelse
A minor change as well in the in you blade template to make use of the #forelse directive for less code.
You could also change your controller code a bit:
return view('admin.posts.edit', compact('post', 'categories'));
Further the laravelcollective/html package might help you a lot in creating forms.