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    Generator::getReturn

    (PHP 7, PHP 8)

    Generator::getReturn — ジェネレータの戻り値を取得する

    説明

    public Generator::getReturn(): mixed

    パラメータ

    この関数にはパラメータはありません。

    戻り値

    ジェネレータの実行が終了すると、その戻り値を返します。

    例

    例1 Generator::getReturn() の例

    <?php

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

    return     3;
    })();

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

    echo     $gen->getReturn(), PHP_EOL;

    上の例の出力は以下となります。

    1
2
3

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    User Contributed Notes 3 notes

    up
    17
    pemapmodder1970 at gmail dot com
    7 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.
    up
    0
    Hayley Watson
    6 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.
    up
    0
    brandon at cryy dot com
    7 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.
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