如果返回值混合使用什么类型的提示? [英] What type hint to use if return value is mixed?

问题描述

function foo ($a): mixed
{
    if ($a == 1)    
        return true;
    else
        return 'foo';
}

var_dump(foo(1));

由于mixed不是实型，因此导致:

Since mixed is not a real type this results to:

致命错误:未捕获的TypeError:foo()的返回值必须为 混合...的实例

Fatal error: Uncaught TypeError: Return value of foo() must be an instance of mixed...

有没有一种方法可以在mixed返回值中键入提示，或者您是否只是在这种情况下不声明类型提示?

Is there a way to type hint a mixed return value or do you simply not declare type hints in this type of scenario?

推荐答案

在那里提供了类型提示，以强制限制传递或返回的值.由于混合"将完全允许任何值，因此将其用作类型提示将毫无意义，因此只需将其忽略即可.

Type hints are there to enforce some restriction on the value passed or returned. Since "mixed" would allow any value at all, its use as a type hint would be pointless, so just omit it.

有人提议在语言中添加联合类型"，这将允许您在示例中将返回类型声明为bool|string，但尚未被接受.

There have been proposals to add "union types" to the language, which would allow you to declare the return type in your example as bool|string, but none has yet been accepted.

您可以做的是在文档块中的 document 函数的返回值. IDE和文档生成器通常会理解语法@return bool|string，然后可以添加为什么的描述，返回类型会有所不同，以及何时期望使用哪种类型.

What you can do is document the return value of your function, in a docblock. IDEs and documentation generators will generally understand the syntax @return bool|string, and you can then add a description of why the return type varies, and when to expect which type.

当然，值得考虑的一个选项是重新考虑您的设计，并提出一个函数，该函数可以传达其结果 而无需针对不同情况返回不同的类型.例如，使用异常代替错误的特殊值，或者将像getThing(boolean $asString): float|string这样的函数拆分为两个函数getThingAsFloat(): float和getThingAsString(): string.

Of course, an option well worth considering is to reconsider your design, and come up with a function which can communicate its result without returning different types for different cases. For instance, using exceptions instead of a special value for errors, or splitting a function like getThing(boolean $asString): float|string into two functions getThingAsFloat(): float and getThingAsString(): string.

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