Laravel Advanced何处将变量传递给函数? [英] Laravel Advanced Wheres how to pass variable into function?

问题描述

文档中的示例

DB::table('users')
        ->whereExists(function($query)
        {
            $query->select(DB::raw(1))
                  ->from('orders')
                  ->whereRaw('orders.user_id = users.id');
        })
        ->get();

但是如果我需要使用这样的外部变量怎么办?

But what if I need to use external variable like that:

            ->where('city_id', '=', $this->city->id)
            ->where(function($query)
                {
                    $query->where('name', 'LIKE', '%'.$searchQuery.'%')
                    ->orWhere('address', 'LIKE', '%'.$searchQuery.'%')

                })

目前，我创建了新属性并通过$this->访问了它，但是还有其他更便捷的方法吗?

For now I created new property and accessed it through $this->, but is there any more convenient way?

推荐答案

您可以使用use关键字将必要的变量从父范围传递到闭包中.

You can pass the necessary variables from the parent scope into the closure with the use keyword.

例如:

DB::table('users')->where(function ($query) use ($activated) {
    $query->where('activated', '=', $activated);
})->get();

有关此处的更多信息.

PHP 7.4(将在 2019年11月28日发布)引入了一个较短的变体称为箭头功能的匿名函数，这使它的详细程度降低了.

PHP 7.4 (will be released at November 28, 2019) introduces a shorter variation of the anonymous functions called arrow functions which makes this a bit less verbose.

使用PHP 7.4的示例，在功能上几乎等效(请参见下面的第3个要点):

An example using PHP 7.4 which is functionally nearly equivalent (see the 3rd bullet point below):

DB::table('users')->where(fn($query) => $query->where('activated', '=', $activated))->get();

与常规语法相比的差异:

Differences compared to the regular syntax:

• fn关键字而不是function.
• 无需显式列出应从父级作用域捕获的所有变量-现在这是自动按值完成的.请参阅后面的示例中缺少use关键字的内容.
• 箭头功能始终返回一个值.这也意味着在声明它们时不可能使用void返回类型.
• 必须省略return关键字 .
• 箭头功能必须具有单个表达式，即return语句.目前不支持多行功能.您仍然可以链接方法.

• fn keyword instead of function.
• No need to explicitly list all variables which should be captured from the parent scope - this is now done automatically by-value. See the lack of use keyword in the latter example.
• Arrow functions always return a value. This also means that it's impossible to use void return type when declaring them.
• The return keyword must be omitted.
• Arrow functions must have a single expression which is the return statement. Multi-line functions aren't supported at the moment. You can still chain methods though.

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