Laravel雄辩地为模型关系设置默认值吗? [英] Laravel Eloquent setting a default value for a model relation?

问题描述

我有两个模型:

class Product extends Eloquent {

    ...

    public function defaultPhoto()
    {
        return $this->belongsTo('Photo');
    }

    public function photos()
    {
        return $this->hasMany('Photo');
    }
}

class Photo extends Eloquent {

    ...

    public function getThumbAttribute() {
        return 'products/' . $this->uri . '/thumb.jpg';
    }

    public function getFullAttribute() {
        return 'products/' . $this->uri . '/full.jpg';
    }

    ...

}

这很好用，我可以调用$product->defaultPhoto->thumb和$product->defaultPhoto->full并获取相关图像的路径，并使用$product->photos并遍历所有值来获取所有照片.

This works fine, I can call $product->defaultPhoto->thumb and $product->defaultPhoto->full and get the path to the related image, and get all photos using $product->photos and looping through the values.

当产品没有照片时就会出现问题，我似乎无法找出一种为这种情况设置默认值的方法.

The problem arises when the product does not have a photo, I can't seem to figure out a way to set a default value for such a scenario.

我尝试做类似的事情

public function photos() 
{
    $photos = $this->hasMany('Photo');
    if ($photos->count() === 0) {
        $p = new Photo;
        $p->url = 'default';
        $photos->add($p);
    }

    return $photos;
}

我还创建了一个全新的Collection来存储新的Photo模型，但是它们都返回相同的错误:

I have also creating a completely new Collection to store the new Photo model in, but they both return the same error:

Call to undefined method Illuminate\Database\Eloquent\Collection::getResults()

有人做过类似的事情吗?

Has anyone done anything similar to this?

提前谢谢！

推荐答案

您可以在对您进行检查的Product模型上创建访问器.如果您只是想将其定义为方法，则其工作原理也相同(也适用于希望抽象化一些Eloquent调用，为产品使用接口，以防以后更改的情况，等等)

You could create an accessor on the Product model that did the check for you. Works the same if you just wanted to define it as a method, also (good for if you want to abstract some of the Eloquent calls, use an interface for your Product in case you change it later, etc.)

/**
 * Create a custom thumbnail "column" accessor to retrieve this product's
 * photo, or a default if it does not have one.
 * 
 * @return string
 */
public function getThumbnailAttribute()
{
    $default = $this->defaultPhoto;

    return ( ! is_null($default))
        ? $default->thumb
        : '/products/default/thumb.jpg';
}

您可能还想研究演示者.在某些情况下有点过大，但是使用起来非常方便(并且将这样的事情从模型中抽象出来).

You might also want to look into Presenters. A bit overkill for some situations, but incredibly handy to have (and abstract things like this away from your models).

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