2.10PHP类型之可迭代(Iterable)类型

iterable 类型是联合类型 array|Traversable 的别名。

1.Traversable接口

这个接口没有任何方法，它的作用仅仅是作为所有可遍历接口的基本接口。

interface Traversable {
}

2.Iterator接口

Iterator接口是Traversable接口的子接口。

interface Iterator extends Traversable {

    /* 方法 */
    public current(): mixed
    public key(): mixed
    public next(): void
    public rewind(): void
    public valid(): bool
}

3.Iterator接口的自定义实现

<?php
class myIterator implements Iterator {
    private $position = 0;
    private $array = array(
        "firstelement",
        "secondelement",
        "lastelement",
    );  

    public function __construct() {
        $this->position = 0;
    }

    public function rewind(): void {
        var_dump(__METHOD__);
        $this->position = 0;
    }

    #[\ReturnTypeWillChange]
    public function current() {
        var_dump(__METHOD__);
        return $this->array[$this->position];
    }

    #[\ReturnTypeWillChange]
    public function key() {
        var_dump(__METHOD__);
        return $this->position;
    }

    public function next(): void {
        var_dump(__METHOD__);
        ++$this->position;
    }

    public function valid(): bool {
        var_dump(__METHOD__);
        return isset($this->array[$this->position]);
    }
}

$it = new myIterator;

foreach($it as $key => $value) {
    var_dump($key, $value);
    echo "\n";
}
?>

//输出
string(18) "myIterator::rewind"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(0)
string(12) "firstelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(1)
string(13) "secondelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"
string(19) "myIterator::current"
string(15) "myIterator::key"
int(2)
string(11) "lastelement"

string(16) "myIterator::next"
string(17) "myIterator::valid"

4.Generator类

PHP内置的Generator类是Iterator接口的实现。

final class Generator implements Iterator {
    
    /* 方法 */
    public current(): mixed
    public getReturn(): mixed
    public key(): mixed
    public next(): void
    public rewind(): void
    public send(mixed $value): mixed
    public throw(Throwable $exception): mixed
    public valid(): bool
    public __wakeup(): void
}