Question

我正在学习amphp。我想使用amphp中的事件循环将同步调用转换为异步调用。我的示例代码使用file_get_contents作为示例阻止调用。

使用同步通话，如下所示：

$uris = [
    "https://google.com/",
    "https://github.com/",
    "https://stackoverflow.com/",
];

$results = [];
foreach ($uris as $uri) {
    var_dump("fetching $uri..");
    $results[$uri] = file_get_contents($uri);
    var_dump("done fetching $uri.");
}

foreach ($results as $uri => $result) {
    var_dump("uri : $uri");
    var_dump("result : " . strlen($result));
}

输出：

string(30) "fetching https://google.com/.."
string(34) "done fetching https://google.com/."
string(30) "fetching https://github.com/.."
string(34) "done fetching https://github.com/."
string(37) "fetching https://stackoverflow.com/.."
string(41) "done fetching https://stackoverflow.com/."
string(25) "uri : https://google.com/"
string(14) "result : 48092"
string(25) "uri : https://github.com/"
string(14) "result : 65749"
string(32) "uri : https://stackoverflow.com/"
string(15) "result : 260394"

我知道有artax可以异步进行呼叫。但是，我想学习如何正确地将阻塞代码转换为异步并发代码（而非并行）。我已经成功地使用amp并行实现了它。

我相信，如果我在amp中异步成功实现了正确的输出，将会是这样：

string(30) "fetching https://google.com/.."
string(30) "fetching https://github.com/.."
string(37) "fetching https://stackoverflow.com/.."
string(34) "done fetching https://google.com/."
string(34) "done fetching https://github.com/."
string(41) "done fetching https://stackoverflow.com/."
string(25) "uri : https://google.com/"
string(14) "result : 48124"
string(25) "uri : https://github.com/"
string(14) "result : 65749"
string(32) "uri : https://stackoverflow.com/"
string(15) "result : 260107"

我尝试使用以下代码：

<?php
require __DIR__ . '/vendor/autoload.php';

use Amp\Loop;
use function Amp\call;

Loop::run(function () {
    $uris = [
        "https://google.com/",
        "https://github.com/",
        "https://stackoverflow.com/",
    ];

    foreach ($uris as $uri) {
        $promises[$uri] = call(function () use ($uri) {
            var_dump("fetching $uri..");
            $result = file_get_contents($uri);
            var_dump("done fetching $uri.");
            yield $result;
        });
    }

    $responses = yield $promises;

    foreach ($responses as $uri => $result) {
        var_dump("uri : $uri");
        var_dump("result : " . strlen($result));
    }
});

不是给我我期望的结果，而是给我这个错误：

string(30) "fetching https://google.com/.."
string(34) "done fetching https://google.com/."
string(30) "fetching https://github.com/.."
string(34) "done fetching https://github.com/."
string(37) "fetching https://stackoverflow.com/.."
string(41) "done fetching https://stackoverflow.com/."
PHP Fatal error:  Uncaught Amp\InvalidYieldError: Unexpected yield; Expected an instance of Amp\Promise or React\Promise\PromiseInterface or an array of such instances; string yielded at key 0 on line 20

结果似乎也同步运行，而不是异步运行。

我应该如何正确做？

Answer 1

您需要使用所使用功能的非阻塞实现。 ssh -l user_pi -p 1234 localhost正在阻止。例如，您可以在file_get_contents中找到非阻塞实现。如果将amphp/file替换为file_get_contents，它应该可以正常工作。

如何在amphp中正确地将闭包变为Promise？

1 个答案: