在PHP中按类(instanceof)切换

Question

可以if( .. instanceof ...), elseif(... instanceof ...), ... 用开关替换块吗？

例如:

<?php
$class = ..... //some class

if($class instanceof SomeClass) {
    //do something
} elseif($class instanceof SomeAnotherClass) {
    //do something else
}

Answer 1

有人喜欢这样:

$class = get_class($objectToTest);

switch($class) {  
    case 'TreeRequest':
        echo "tree request";
        break;
    case 'GroundRequest':
        echo "ground request";
        break;
}

或这个:

switch(true) {  
    case $objectToTest instanceof TreeRequest:
        echo "tree request";
        break;
    case $objectToTest instanceof GroundRequest:
        echo "ground request";
        break;
}

Answer 2

以下更正确:

$class = get_class($objectToTest);

switch($class) {  
    case TreeRequest::class:
        echo "tree request";
        break;
    case GroundRequest::class:
        echo "ground request";
        break;
}

这样就可以正确地比较命名空间(你不必输入它们),如果有任何变化,例如命名空间或类名,你会得到一个体面的IDE错误,通知你代码被破坏了.

Answer 3

使用match表达式，它看起来像这样：

return match(get_class($object)) {  
   TreeRequest::class => "tree request",
   GroundRequest::class => "ground request",
   default => "default request"
};

请记住，它错过了继承并且仅采用当前类。考虑继承的匹配表达式：

return match(true) {  
   $object instanceof TreeRequest=> "tree request",
   $object instanceof GroundRequest => "ground request",
   default => "default request"
};