在Laravel中保存模型时出错。 “在非对象上调用成员函数getKey（）”

Question

I try save my object in DB by this code:

$preview = new ProjectProductPreview();
$preview->user_id = $user_id;
$preview->path = $preview_url;
$preview->type = $type;
$preview->project_product_id = $product_id;
$preview->save();  

And I got strange error. This error occurs when call save() method. I have checked my laravel logs, there is this error. I can debug this precisely because in this case, error stack has only two positions

[2015-02-17 09:37:30] production.ERROR: exception 'Symfony\Component\Debug\Exception\FatalErrorException' with message 'Call to a member function getKey() on a non-object' in /var/www/erp/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Collection.php:133
    Stack trace:
    #0 [internal function]: Illuminate\Exception\Handler->handleShutdown()
    #1 {main} [] []

My model looks like:

class ProjectProductPreview extends BaseModel {

    protected $table = 'project_products_preview';


    public function user() {
        return $this->belongsTo('User');
    }

    public function project_product() {
        return $this->belongsTo('ProjectProduct', 'project_product_id');
    }

    public function projectProduct()
    {
        return $this->belongsTo('ProjectProduct', 'project_product_id');
    }

    public function message() {
        return $this->belongsToMany('Message');
    }

    public function getThumb() {
        $path = $this->path;
        $thumb_path = str_replace('.jpg', '_70.jpg', $path);
        return $thumb_path;
    }

    public function fullPath() {
        return public_path($this->path);
    }

    public function getPath()
    {
        return $this->path;
    }

    public function getUrlAttribute() {
        $product_id = $this->project_product_id;

        return '/product/' . $product_id . '#' . $this->id;
    }

    public function isAccepted()
    {
        if($this->accepted==1){
            return true;
        }

        return false;
    }

    public function accept()
    {
        ProjectProductPreview::where('project_product_id',$this->project_product_id)->update(array('accepted'=>0));
        $this->accepted=1;
        $this->save();

        Event::fire('project_product_preview.accepted', array($this));
    }

    public function acceptRemove()
    {
        $this->accepted=0;
        $this->save();

        Event::fire('project_product_preview.remove_accept', array($this));
    }

}

Answer 1

I am not quite sure about this, but I think this line

$preview->project_product_id = $product_id;

causes the issue. You have a relationship to ProjectProduct so you might want to do sth. like that actually:

$preview->projectProduct()->associate(ProjectProduct::find($product_id));

see the laravel docs on inserting models . Please also note that you have two identical realtionships to ProjectProduct which might cause unexpected behaviour as well. At least one is superflous.

// one can be removed
//public function project_product() {
//    return $this->belongsTo('ProjectProduct', 'project_product_id');
//}

public function projectProduct()
{
    return $this->belongsTo('ProjectProduct', 'project_product_id');
}