Many to many insertion error Call to a member function Laravel 5.5

I have a trouble in many to many insertion. My code in controller is right. After I add the two data which is successful, the third time I try to insert produce an error:

Call to a member function bagcollects() on null

and the error is on this code

$collection->bagcollects()->attach($bagcollect->id);


I just don't understand why this error occurred!

I'll show the whole code of CollectionsController store method:

public function addbag(Request $request)
$collection = Collection::find($request->input('collection_id'));
$bagcollect = Bagcollect::create([
'bag_id' => $request->input('bag_id'),
'weight' => $request->input('weight')
]);
$collection->bagcollects()->attach($bagcollect->id);
return redirect()->route('collections.show', ['collection'=> $collection->id]);



Migration on collections

Schema::disableForeignKeyConstraints();
if(!Schema::hasTable('collections'))
Schema::create('collections', function (Blueprint $table)
$table->engine = "InnoDB";
$table->increments('id');
$table->integer('assignment_id')->unsigned();
$table->foreign('assignment_id')->references('id')->on('assignments')->onUpdate('cascade')->onDelete('cascade');
$table->timestamp('collected_on');
);



Migration on bagcollects

Schema::create('bagcollects', function (Blueprint $table)
$table->engine = "InnoDB";
$table->increments('id');
$table->integer('bag_id')->unsigned();
$table->double('weight', 8, 2);
$table->foreign('bag_id')->references('id')->on('bags');
$table->timestamps();
);


Migration bagcollect_collection

Schema::create('bagcollect_collection', function (Blueprint $table)
$table->engine = "InnoDB";
$table->increments('id');
$table->integer('bagcollect_id')->unsigned();
$table->integer('collection_id')->unsigned();
$table->foreign('bagcollect_id')->references('id')->on('bagcollects');
$table->foreign('collection_id')->references('id')->on('collections');
$table->timestamps();
);


collections show.blade.php add modal

<!-- ADD MODAL -->
<div class="modal fade" role="dialog" id="addModal">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal">&times;</button>
<h4 class="modal-title">New Collection</h4>
</div>

<div class="modal-body">
<div class="row">
<div class="col-md-12">
<form class="form-horizontal" method="POST" action=" route('collections.addbag') ">
csrf_field()


<div class="row form-group">

<input class="form-control" name = "collection_id" id="collection_id" value="$collection->id" type="hidden">
<div class=" $errors->has('bag') ? ' has-error' : '' ">
<div class="col-md-8">
<label for="bag_id">Bag</label>
<select class="form-control" required id="bag" name="bag_id">
<option value="" data-hidden="true"
selected="selected">
</option>
@foreach($bags as $bag)
<option value= " $bag->id ">
$bag->name
</option>
@endforeach
</select>
</div>
</div>

<div class=" $errors->has('weight') ? ' has-error' : '' ">
<div class="col-md-8">
<label for="weight">Weight</label>
<input type="text" class="form-control" id="weight" name= "weight" required>
</div>
</div>

</div>

<!-- SUBMIT BUTTON -->
<button type="submit" class="btn btn-success btn-fill pull-right" id="form-button-add">
Create
</button>

<button data-dismiss="modal" aria-hidden="true" class="btn btn-basic pull-right" style="margin-right: 2%">
Cancel
</button>
<div class="clearfix"></div>

</form>
</div>
</div>
</div>
</div>
</div>
</div>


Collection.php model

protected $fillable = [
'id',
'assignment_id',
'bag_id'
];

public $timestamps = false;

public function assignment()

return $this->belongsTo('AppAssignment');


public function bagcollects()

return $this->belongsToMany('AppBagcollect');



Bagcollect.php

protected $fillable = [
'bag_id',
'weight'
];

public function collections()

return $this->belongsToMany('AppCollection');


public function bag()

return $this->belongsTo('AppBag');



BagcollectCollection.php

protected $table = "bagcollect_collection";

protected $fillable = [
'bagcollect_id',
'collection_id',

];


Collection

Collection

Collection

use

$collection

1 Answer
1

Call to a member function ... on null

null

Means that you're trying to call a function on a null object. Review your code:

null

$collection = Collection::find($request->input('collection_id'));


With your current logic, $collection could be null, so calling

$collection

null

$collection->bagcollects() ...


Will throw this error.

Debug the result of Collection::find(...) and ensure that $collection is not null.

Collection::find(...)

$collection

null

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