Type-hint closure parameters

问题

With type-hinting in PHP is it possible to type-hint the parameters of a closure?

for example

function some_function(\Closure<int> $closure) {
    $closure(3);
}

// This would throw an exception
some_function(function(string $value) {
    echo $value;
});

// This would work.
some_function(function(int $value) {
    echo $value;
});

回答1:

Not natively. You would need to manually make use of reflection.

<?php
function some_function(\Closure $closure) {

    $reflection = new ReflectionFunction($closure);
    $parameters = $reflection->getParameters();
    if(!isset($parameters[0]))
    {
        // I'm lazy but you should program this to throw a fatal exception
        echo 'some_function() expects parameter one\'s closure to expect at least one parameter'.PHP_EOL;
    }
    elseif($parameters[0]->getType().'' !== 'int') // I'm sure there is a more elegant way to achieve this...
    {
        // I'm lazy but you should program this to throw a fatal exception
        echo 'closure\'s first param should be an int'.PHP_EOL;
    }
    else
    {
        $closure(3);
    }
}

// Does not throw an exception
some_function(function(int $value) {
    var_dump($value);
});

// This throws an exception
some_function(function() {
    var_dump($value);
});

// This throws an exception
some_function(function(string $value) {
    var_dump($value);
});

Produces:

int(3)
some_function() expects parameter one's closure to expect at least one parameter
closure's first param should be an int

Also see Deducing PHP Closure parameters

来源：https://stackoverflow.com/questions/56809237/type-hint-closure-parameters

标签

php

closures

type-hinting