调用未定义的方法Illuminate \\ Database \\ Query \\ Builder :: attach（）在laravel 5.3中

Question

I need help with this error

Call to undefined method Illuminate\\Database\\Query\\Builder::attach()

my Model is

public function casts()
{
    return $this->belongsToMany(Cast::class)->withTimestamps();
}

My Controller

public function addCast(Request $request, $id)
{
    $this->validate($request, [
        'casts' => 'required'
    ]);
    $show = $this->shows->findOrFail($id);
    $show->photos()->attach($request->input('casts'));
    dd($show);

}

my Form

 <form action="{{ route('shows.addCasts', $show->id) }}" method="POST">
            {{ csrf_field() }}
        <div class="modal-header">
            <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                <span aria-hidden="true">&times;</span>
            </button>
            <h4 class="modal-title"><img src="{{ Storage::url($show->small_image) }}" height="30" width="30">{{ $show->name }}</h4>
        </div>
        <div class="modal-body">
            <div class="form-group">
                {!! Form::label('casts') !!}
                {{ Form::select('casts[]', $casts, null, ['class' => 'form-control roles']) }}
            </div>
        </div>
        <div class="modal-footer">
            <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
            {!! Form::submit('Save Cast', ['class' => 'btn btn-primary']) !!}
            {{--<button type="submit" class="btn btn-primary">Save changes</button>--}}
        </div>
        </form>

can anybody tell my what i did wrong or if you guys have any solution Thank for your help

Answer 1

The other side of the relationship also needs to be a belongsToMany as the attach method is for many to many relationships - see an already answered post on this:

"Many to many - attach"