Laravel + 可为空的外键
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Laravel + nullable foreign keys
提问by mpen
I've got a form with a dropdown selection that lets you choose a foreign key for a particular model. The top option is always something like
我有一个带有下拉选项的表单，可让您为特定模型选择外键。最上面的选项总是像
<option value="">please select</option>
So when I fill my model with this data from the form,
所以当我用表单中的数据填充我的模型时，
$booking = new Booking($data);
And try to save it,
并尝试保存它，
$booking->save();
It always fails because that violates the FK constraint because Laravel isn't smart enough to nullify this field for me. Thus I came up with this little hack:
它总是失败，因为这违反了 FK 约束，因为 Laravel 不够聪明，无法为我取消这个字段。因此我想出了这个小技巧：
public function save() {
if(!$this->vehicle_id) $this->vehicle_id = null;
if(!$this->driver_id) $this->driver_id = null;
parent::save();
}
But is there no way to tell Laravel which fields represent FKs and should be set to null if they an integer > 0?
但是有没有办法告诉 Laravel 哪些字段代表 FK，如果它们的整数 > 0 应该设置为 null？
回答by mpen
One possible solution is to use set mutatorsfor all your foreign keys:
一种可能的解决方案是对所有外键使用set mutators：
public function setVehicleIdAttribute($value) {
$this->attributes['vehicle_id'] = $value ?: null;
}
public function setDriverIdAttribute($value) {
$this->attributes['driver_id'] = $value ?: null;
}
