Laravel 检查收集是否为空

To determine if there are any results you can do any of the following:

if ($mentor->first()) { }
if (!$mentor->isEmpty()) { }
if ($mentor->count()) { }
if (count($mentor)) { }
if ($mentor->isNotEmpty()) { }

Notes / References

->first()

https://laravel.com/api/5.7/Illuminate/Database/Eloquent/Collection.html#method_first

isEmpty() https://laravel.com/api/5.7/Illuminate/Database/Eloquent/Collection.html#method_isEmpty

->count()

https://laravel.com/api/5.7/Illuminate/Database/Eloquent/Collection.html#method_count

count($mentors) works because the Collection implements Countable and an internal count() method:

https://laravel.com/api/5.7/Illuminate/Database/Eloquent/Collection.html#method_count

isNotEmpty()

https://laravel.com/docs/5.7/collections#method-isnotempty

So what you can do is :

if (!$mentors->intern->employee->isEmpty()) { }

You can always count the collection. For example $mentor->intern->count() will return how many intern does a mentor have.

https://laravel.com/docs/5.2/collections#method-count

In your code you can do something like this

foreach($mentors as $mentor)
@if($mentor->intern->count() > 0)
@foreach($mentor->intern as $intern)
<tr class="table-row-link" data-href="/werknemer/{!! $intern->employee->EmployeeId !!}">
<td>\{\{ $intern->employee->FirstName }}</td>
<td>\{\{  $intern->employee->LastName }}</td>
</tr>
@endforeach
@else
Mentor don't have any intern
@endif
@endforeach

This is the fastest way:

if ($coll->isEmpty()) {...}

Other solutions like count do a bit more than you need which costs slightly more time.

Plus, the isEmpty() name quite precisely describes what you want to check there so your code will be more readable.

Starting from Laravel 5.3 you can simply use :

if ($mentor->isNotEmpty()) {
//do something.
}

Documentation https://laravel.com/docs/5.5/collections#method-isnotempty

I prefer

(!$mentor)

Is more effective and accurate

From php7 you can use Null Coalesce Opperator:

$employee = $mentors->intern ?? $mentors->intern->employee

This will return Null or the employee.

This is the best solution I found so far.

in blade

@if($mentors->count() == 0)
<td colspan="5" class="text-center">
Nothing Found
</td>
@endif

in controller

if ($mentors->count() == 0) {
return "Nothing Found";
}

First you can convert your collection to an array. Next run an empty method like this:

if(empty($collect->toArray())){}