Laravel 检查相关模型是否存在 [英] Laravel Check If Related Model Exists

问题描述

我有一个 Eloquent 模型，它有一个相关的模型:

I have an Eloquent model which has a related model:

public function option() {
    return $this->hasOne('RepairOption', 'repair_item_id');
}

public function setOptionArrayAttribute($values)
{
    $this->option->update($values);
}

当我创建模型时，它不一定有相关模型.当我更新它时，我可能会添加一个选项，也可能不添加.

When I create the model, it does not necessarily have a related model. When I update it, I might add an option, or not.

所以我需要检查相关模型是否存在，分别更新它或创建它:

So I need to check if the related model exists, to either update it, or create it, respectively:

$model = RepairItem::find($id);
if (Input::has('option')) {
    if (<related_model_exists>) {
        $option = new RepairOption(Input::get('option'));
        $option->repairItem()->associate($model);
        $option->save();
        $model->fill(Input::except('option');
    } else {
       $model->update(Input::all());
    }
};

其中 是我要查找的代码.

Where <related_model_exists> is the code I am looking for.

推荐答案

在 php 7.2+ 中你不能在关系对象上使用 count，所以没有一个-适合所有关系的所有方法.使用下面提供的@tremby 查询方法:

In php 7.2+ you can't use count on the relation object, so there's no one-fits-all method for all relations. Use query method instead as @tremby provided below:

$model->relation()->exists()

<小时>

适用于所有关系类型的通用解决方案(pre php 7.2):

if (count($model->relation))
{
  // exists
}

这将适用于每个关系，因为动态属性返回 Model 或 Collection.两者都实现了ArrayAccess.

This will work for every relation since dynamic properties return Model or Collection. Both implement ArrayAccess.

事情是这样的:

单一关系: hasOne/belongsTo/morphTo/morphOne

// no related model
$model->relation; // null
count($model->relation); // 0 evaluates to false

// there is one
$model->relation; // Eloquent Model
count($model->relation); // 1 evaluates to true

对多关系: hasMany/belongsToMany/morphMany/morphToMany/morphedByMany

// no related collection
$model->relation; // Collection with 0 items evaluates to true
count($model->relation); // 0 evaluates to false

// there are related models
$model->relation; // Collection with 1 or more items, evaluates to true as well
count($model->relation); // int > 0 that evaluates to true

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