使用object属性作为method属性的默认值

I'm trying to do this (which produces an unexpected T_VARIABLE error):

我正在尝试这样做（产生意外的T_VARIABLE错误）：

public function createShipment($startZip, $endZip, $weight = $this->getDefaultWeight()){}

I don't want to put a magic number in there for weight, since the object I am using has a "defaultWeight" parameter that all new shipments get if you don't specify a weight. I can't put the defaultWeight in the shipment itself, because it changes from shipment group to shipment group. Is there a better way to do it than the following?

我不想在那里放一个幻数来表示重量，因为我使用的对象有一个“defaultWeight”参数，如果你没有指定一个重量，所有新货都会得到。我无法将defaultWeight放入货件本身，因为它从货件组更改为货件组。有没有比以下更好的方法呢？

public function createShipment($startZip, $endZip, weight = 0){
    if($weight <= 0){
        $weight = $this->getDefaultWeight();
    }
}

4 个解决方案

#1

This isn't much better:

这不是更好：

public function createShipment($startZip, $endZip, $weight=null){
    $weight = !$weight ? $this->getDefaultWeight() : $weight;
}

// or...

public function createShipment($startZip, $endZip, $weight=null){
    if ( !$weight )
        $weight = $this->getDefaultWeight();
}

#2

Neat trick with boolean OR operator:

使用布尔OR运算符的巧妙技巧：

public function createShipment($startZip, $endZip, $weight = 0){
    $weight or $weight = $this->getDefaultWeight();
    ...
}

#3

This will allow you to pass a weight of 0 and still work properly. Notice the === operator, this checks to see if weight matches "null" in both value and type (as opposed to ==, which is just value, so 0 == null == false).

这将允许您传递0的权重，仍然可以正常工作。注意===运算符，它检查重量是否与值和类型中的“null”匹配（与==相反，这只是值，因此0 == null == false）。

PHP:

PHP：

public function createShipment($startZip, $endZip, $weight=null){
    if ($weight === null)
        $weight = $this->getDefaultWeight();
}

#4

You can use a static class member to hold the default:

您可以使用静态类成员来保存默认值：

class Shipment
{
    public static $DefaultWeight = '0';
    public function createShipment($startZip,$endZip,$weight=Shipment::DefaultWeight) {
        // your function
    }
}

#1