function* powGenerator() {
var result = Math.pow(yield "a",yield "b");
return result;
}
var g = powGenerator();
console.log(g.next().value); // "a",from the first yield
console.log(g.next(10).value); // "b",from the second
console.log(g.next(2).value); // 100,the result
我正在尝试使用类似于PHP的模型,但这有点令人头疼.
<?PHP function powGenerator() { return pow((yield 'a'),(yield 'b')); }
Fatal error: Generators cannot return values using “return”
好吧,也许我会用另一个产量来获得最终价值？ …
<?PHP function powGenerator() { yield pow((yield 'a'),(yield 'b')); } $g = powGenerator(); //=> Generator {#180} echo $g->send(10); //=> "b" echo $g->send(2); //=> 100
好的,所以我恢复了价值,但这里有两个主要问题
>我的“a”去了哪里？ – 注意在JS示例中,我能够访问“a”和“b”产生的值以及100个最终结果.
>发电机还没有完成！ – 我必须拨打额外的时间来完成发电机
$g->valid(); //=> true
$g->send('?'); //=> null
$g->valid(); //=> false
public mixed Generator::send ( mixed $value )Sends the given value to the generator as the result of the current
yieldexpression and resumes execution of the generator.If the generator is not at a
yieldexpression when this method is called,it will first be let to advance to the firstyieldexpression before sending the value. As such it is not necessary to “prime” PHP generators with a 07002 call (like it is done in Python).
强调“因此没有必要使用Generator :: next()来”启动“PHP生成器”.好的,但这究竟意味着什么？我没有像JavaScript示例那样“填充”它,但是第一个产生的值也被吞噬了.
任何人都可以解释你是如何在不使用foreach的情况下逐步完成生成器的吗？
$g = powGenerator(); echo $g->current(); //a
你然后两次发送值并恢复执行,$g-> valid()在此之后为真,因为你没有在第三次收益后恢复 – 发电机不完整而且可能还有更多要做的事情.考虑：
function powGenerator() {
yield pow((yield 'a'),(yield 'b'));
echo "Okay,finishing here now!\n";
}
$g = powGenerator();
echo $g->current(),"\n"; //a
echo $g->send(10),"\n"; //b
echo $g->send(2),"\n"; //100
$g->next(); // Resumes execution of the generator,// which prints its own message and completes.
var_dump($g->valid()); //false
这个’输出：
a b 100 Okay,finishing here now! bool(false)
现在在PHP 7中你可以return from a generator.
function powGenerator() {
return pow((yield 'a'),(yield 'b'));
echo "This will never print.";
}
$g = powGenerator();
echo $g->current(),"\n"; // Prints just the newline,you're moving on
// to a return which you must get explicitly.
var_dump($g->valid()); // Generator complete,you're free to get the return.
echo $g->getReturn(),"\n";
哪个输出：
a b bool(false) 100
至于在没有foreach的情况下单步执行它们 – Generator实现了Iterator,所以它有适当的方法来处理它：current,key,next,rewind和valid.有一点需要注意,如果你调用它,它将引发异常已经开始的发电机.
这样做的一个例子也演示了PHP 7的新generator delegation：
function letterGenerator() {
yield from range('a','z');
}
$g = letterGenerator();
while ($g->valid()) {
echo $g->current();
$g->next();
}
输出：
abcdefghijklmnopqrstuvwxyz
