Laravel.如何查找具有特定最新相关模型的模型 [英] Laravel. How to find models which has specific latest related model

问题描述

Laravel 5.3.

Laravel 5.3.

包模型具有许多步骤模型. 步骤模型有一个名为status的列，其类型为tiny int，而为created_at列. 例如，包A具有以下步骤:

A Package Model has many Step Models. The Step Model has a column calls status whose type is tiny int and created_at column. For example, a package A, has these steps:

• 十月. 18 10:00，状态1
• 十月. 19 09:00，状态2

而且，程序包B具有以下步骤:

And, a package B, has these steps:

• 十月. 19 08:00，状态1
• 十月. 19 09:00，状态2
• 十月. 19 10:00，状态3

就像这样，很多软件包，每个软件包都有很多步骤.

Just like that, many packages, each of them has many steps.

A的最新步骤的状态为2，而B的最新状态为3

A's latest step's status is 2 and B's is 3

我的问题是，如何找到最新步骤状态为2的软件包?预期结果是软件包的集合，在此示例中，应包含A.

My problem is, how to find Packages whose latest step status is 2? The expected result is a collection of packages, in this example, should contains A.

我尝试将其添加到我的包装模型中.

I have tried add this in my Package Model.

public function steps()
{
    return $this->hasMany('App\Step');
}

public function status()
{
    return $this->steps()->latest()->limit(1);
}

并使用

Package::whereHas('status', function ($q) {
    $q->where('status', 2);
})->get();

但无法获得预期的结果.

but can't get expected result.

没想到的是，如果Packages Table仅包含1行，则Package B的预期结果是一个空集合.但它返回包含B的集合.

What not expected is, if Packages Table has only 1 row, the Package B, expected result is an empty collection. But it return a collection contains B.

我也尝试过将Package Model中的状态功能更新为

I have also tried update the status function in Package Model to

public function status()
{
    return $this->hasOne('App\Step')->latest();
}

但它仍然无法正常工作.

but it still not work.

那么，正确的方法是什么?谢谢你.

So, what is the right way? Huge thank to you.

推荐答案

这很有挑战性.我想不出一种解决方案，可以通过执行一个雄辩的查询来实现所需的功能.但是我发现了一种可以通过两个步骤为您提供结果的方法-即查询+过滤器.

This is quite challenging. I couldn't think of a solution that you can achieve what you want by doing a single Eloquent query. However I found a way that gives you the result in two steps - i.e. query + filter.

但是在此之前，您需要为Package模型添加范围:

But before that you need to add a scope to your Package model:

public function scopeOfStatus($query, $status)
{
    return $query->whereHas('steps', function($q) use ($status) 
    {
        $q->where('status', $status);   
    });
}

第1步:编写查询以检索至少与您的给定状态相匹配至少一步的所有软件包:

Step 1: Write a query that retrieves all packages with at least one step matching your given status:

$status = 1;
$packages = Package::with('steps')->ofStatus($status)->get();

第2步::过滤结果以仅获取最后一步与您的给定状态相匹配的软件包:

Step 2: Filter the result to get only packages which their last step matches your given status:

$packages = $packages->filter(function($package) use ($status)
{
    return $package->steps->last()->status == $status;
});

最终结果是其最后一步具有status == 1

The final result is a collection of all packages that their last step has status == 1

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