Generator::getReturn

(PHP 7, PHP 8)

Generator::getReturn — 获取生成器的返回值

说明

public Generator::getReturn(): mixed

参数

此函数没有参数。

返回值

在生成器执行完成后，获取生成器的 return 值。

范例

示例 #1 Generator::getReturn() 示例


<?php

$gen = (function() {
    yield 1;
    yield 2;

    return 3;
})();

foreach ($gen as $val) {
    echo $val, PHP_EOL;
}

echo $gen->getReturn(), PHP_EOL;

以上例程会输出：

1
2
3

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User Contributed Notes 4 notes

down

pemapmodder1970 at gmail dot com ¶

4 years ago


The note by jm at guide42 dot com is inaccurate. Generator::getReturn() does not check the existence of the return statement, but rather whether the function has returned (finished executing).

<?php
function f(){
  yield;
}

f()->getReturn(); // Exception: Cannot get return value of a generator that hasn't returned

$f = f();
$f->next(); // NULL
$f->getReturn(); // NULL, because having no return statement implies an empty `return;`, and the void return value is resolved to null.

down

brandon at cryy dot com ¶

4 years ago


I'm not quite sure -- I feel there is an ambiguity issue here with returning a value inside a generator and ->getReturn() method of such generator as I have been able to return an array of sorts, something like this:

function dequeue(){
try{
  foreach($this->buffer->data as $data){ ... }
}
  return $statistics;
}

foreach(($generator = $this->dequeue()) as $bdata){
.....
}

if($statistics = $generator->getReturn()){
 // generator returns $statistics
}

Obviously this is not a complete example, but $statistics does become available with the returned array.

down

-2

Hayley Watson ¶

3 years ago


Just to be clear, the value returned by a generator is not yielded while it is running, but is available afterwards through the getReturn() method.

One use for this could be to record the output of a generator so that it can be iterated over again without having to reconstruct and re-run the generator. (Indeed, one could write a generator that simply does exactly this for any given iterable.)

<?php
function generate_squares($n)
{
    $record = [];
    for($i = 0; $i <= $n; ++$i)
    {
        yield ($record[] = $i * $i);
    }
    return $record;
}

$squares = generate_squares(10);
foreach($squares as $s)
{
    echo $s, ' ';
}
$recorded = $squares->getReturn();
echo "\nThat's [", join(', ', $recorded), "]";
?>

Recording keys as well would take a bit more work, as generators are free to repeat them but arrays aren't.

down

-11

jm at guide42 dot com ¶

5 years ago


Be careful that `->getReturn()` will throw an exception if no return is present in the generator:

<?php
function g() {
    yield 'A';
}
try {
    g()->getReturn();
} catch (Exception $ex) {
    var_dump($ex->getMessage());
    // Cannot get return value of a generator that hasn't returned
}
?>

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官方地址：https://www.php.net/manual/en/generator.getreturn.php

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PHP官方手册 - 互联网笔记

Generator::getReturn

说明

参数

返回值

范例

User Contributed Notes 4 notes