Question

function convert($currencyType)
{
    $that = $this;
    return $result = function () use ($that) 
    {
        if (!in_array($currencyType, $this->ratio))
                return false;

        return ($this->ratio[$currencyType] * $this->money); //a float number
    };
}

$currency = new Currency();
echo $currency->convert('EURO');

怎么了？

我收到错误消息：

Catchable fatal error: Object of class Closure could not be converted to string

Answer 1

几个问题：

因为你要返回一个闭包，你必须首先将闭包赋值给变量，然后调用函数
您的$this引用在封闭内不起作用（这就是您use $that代替的原因
您还需要使用$currencyType在闭包的范围内访问它

function convert($currencyType)
{
    $that =& $this; // Assign by reference here!
    return $result = function () use ($that, $currencyType) // Don't forget to actually use $that
    {
        if (!in_array($currencyType, $that->ratio))
                return false;

        return ($that->ratio[$currencyType] * $that->money); //a float number
    };
}

$currency = new Currency();
$convert = $currency->convert('EURO');
echo $convert(); // You're not actually calling the closure until here!

Answer 2

您必须在括号之间创建函数并在关闭函数时添加括号。

function convert($currencyType)
{
    $that = $this;
    return $result = (function () use ($that) 
    {
        if (!in_array($currencyType, $this->ratio))
                return false;

        return ($this->ratio[$currencyType] * $this->money); //a float number
    })();
}

$currency = new Currency();
echo $currency->convert('EURO');

Answer 3

只需删除return并执行：

$result = function () use ($that) 
{
    if (!in_array($currencyType, $this->ratio))
            return false;

    return ($this->ratio[$currencyType] * $this->money); //a float number
};
return $result();

另外，您是否意识到您在功能中没有使用$that？

顺便问一下，为什么你需要匿名功能呢？只是做：

function convert($currencyType)
{
    if (!in_array($currencyType, $this->ratio))
        return false;

    return ($this->ratio[$currencyType] * $this->money); //a float number
}

Answer 4

class Currency {
    function convert($currencyType)
    {
        if (!in_array($currencyType, $this->ratio))
             return false;
        return ($this->ratio[$currencyType] * $this->money); //a float number
    }
}

$currency = new Currency();
echo $currency->convert('EURO');

您正在定义一个lambda函数。你不需要它。此外，如果要有任何准确性，您应该使用bcmul(); PHP中的浮点数将为您带来时髦的结果。

无法将类Closure的对象转换为string：filename。

4 个答案: