如何在php的回调函数中传递参数? [英] How to pass argument in callback function in php?

问题描述

我有一个Repository类，其方法如下:

I have Repository class with a method as follows:

public function GetOne($id){
    $method = __METHOD__;
    $post = null;


    $post = $this->CacheManager($method, function($id) {
        return DB::select("select * from posts where id = ?", [$id]);
    });

    return $post;
}

我想缓存结果，但是在闭包/回调函数中，$ id参数不起作用. CacheManager是我在存储库中使用它的一个特征.

I want to cache the result, but in the closure/callback function the $id parameter is not working. The CacheManager is a trait where I'm using it in my repository.

public function CacheManager($method, $fn) {
  $obj = null;

  if(!$this->HasCache($method)){
    $obj = $fn();
  }else {
    $obj = $this->GetCache($method);
  }

  return $obj;
}

我还有其他一些没有参数的方法，它们正在按预期方式工作.

I have some other methods without parameters and they're working as intended.

推荐答案

使用 use . :D

Use use. :D

使用use子句，可以将变量从父作用域导入到函数的作用域中.

With the use clause, you can import variables from the parent scope into the scope of the function.

public function GetOne($id){
    $method = __METHOD__;
    $post = null;


    $post = $this->CacheManager($method, function() use ($id) {
        return DB::select("select * from posts where id = ?", [$id]);
    });

    return $post;
}

只是一个旁注.由于看起来您正在构建缓存机制，因此您还需要在缓存中包括该ID.当前，您仅按$method进行检查，但是对于每个id，您可能会有一个不同的缓存条目，该缓存条目可能存在或可能不存在.因此，我认为在您的函数中，您需要执行以下操作，以使缓存键更具唯一性.我也将参数$method称为$cacheKey之类的东西，因为它不应该链接到方法本身的名称到缓存.

Just a side note. Since it looks you are building a caching mechanism, you will need to include the ID in the cache as well. Currently you only check by $method, but for each id you will probably have a different cache entry which may or may not exist. So I think in your function you need to do something like the line below to make the cache key more unique. I would also call the parameter $method something like $cacheKey instead, since to the cache it shouldn't be linked to a method name per se.

$method = __METHOD__ . ";$id";

PHP 7.4的更新:箭头功能

用于箭头功能的RFC (又称简短关闭")已通过投票.

The RFC for arrow functions (AKA 'short closures') has passed voting.

对于这些参数，您无需指定要关闭的参数，因为它们始终只能具有一个表达式，因此，它们使用的任何表达式/值都可以(并将)取自父函数范围.

With these you don't specify the parameters you want to close in, because they can only have a single expression anyway, so any expression/value they use can (and will) be taken from the parent function scope.

由于在这种情况下，匿名函数只有一个语句，因此可以将其重写为箭头函数.然后，对缓存管理器的调用将如下所示:

Since in this case the anonymous function just has a single statement, it can be rewritten into an arrow function. The call to the cache manager will then look like this:

public function GetOne($id){
    $method = __METHOD__;
    $post = null;

    $post = $this->CacheManager($method, fn() => DB::select("select * from posts where id = ?", [$id]));

    return $post;
}

这篇关于如何在php的回调函数中传递参数?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！