php switch case语句来处理范围

Question

我正在解析一些文本并根据一些规则计算权重。所有角色的权重都相同。这会使 switch 语句很长我可以在 case 语句中使用范围吗？

我看到一个提倡关联数组的答案。

$weights = array(
[a-z][A-Z] => 10,
[0-9] => 100,
['+','-','/','*'] => 250
);
//there are more rules which have been left out for the sake of clarity and brevity
$total_weight = 0;
foreach ($text as $character)
{
  $total_weight += $weight[$character];
}
echo $weight;

实现这样的目标的最佳方法是什么？ 有没有类似于 php 中的 bash case 语句的东西？ 在关联数组或 switch 语句中写下每个单独的字符肯定不是最优雅的解决方案，还是唯一的选择？

Answer 1

好吧，你可以在 switch 语句中设置范围，例如：

//just an example, though
$t = "2000";
switch (true) {
  case  ($t < "1000"):
    alert("t is less than 1000");
  break
  case  ($t < "1801"):
    alert("t is less than 1801");
  break
  default:
    alert("t is greater than 1800")
}

//OR
switch(true) {
   case in_array($t, range(0,20)): //the range from range of 0-20
      echo "1";
   break;
   case in_array($t, range(21,40)): //range of 21-40
      echo "2";
   break;
}

Answer 2

$str = 'This is a test 123 + 3';

$patterns = array (
    '/[a-zA-Z]/' => 10,
    '/[0-9]/'   => 100,
    '/[\+\-\/\*]/' => 250
);

$weight_total = 0;
foreach ($patterns as $pattern => $weight)
{
    $weight_total += $weight * preg_match_all ($pattern, $str, $match);;
}

echo $weight_total;

*更新：使用默认值 *

foreach ($patterns as $pattern => $weight)
{
    $match_found = preg_match_all ($pattern, $str, $match);
    if ($match_found)
    {
        $weight_total += $weight * $match_found;
    }
    else
    {
        $weight_total += 5; // weight by default
    }
}

Answer 3

您可以使用正则表达式指定字符范围。这样可以避免编写非常长的 switch case 列表。例如，

function find_weight($ch, $arr) {
    foreach ($arr as $pat => $weight) {
        if (preg_match($pat, $ch)) {
            return $weight;
        }   
    }   
    return 0;
}

$weights = array(
'/[a-zA-Z]/' => 10, 
'/[0-9]/'    => 100,
'/[+\\-\\/*]/'   => 250 
);
//there are more rules which have been left out for the sake of clarity and brevity
$total_weight = 0;
$text = 'a1-';
foreach (str_split($text) as $character)
{
  $total_weight += find_weight($character, $weights);
}
echo $total_weight; //360

Answer 4

很多不同的方法来做到这一点。

 $var = 0;
 $range_const = range(10,20);
 switch ($var) {
    case 1: $do = 5; break; # 1
    case 2: $do = 10; break; # 2
    case 3:
    case 4:
    case 5: $do = 15; break; # 3, 4, 5
    default:
      if ($var > 5 && $var < 10) { # High performance (6..9)
        $do = 20;
      } else if (in_array($var, $range_const, true)) { # Looks clear (10..20)
        $do = 25;
      } else { # NOT in range 1..20
        $do = -1;
      }
}
print($do);

没有直接范围 X..Y 比较，因为 $var 在每一步都检查为真，但这允许像这样做一些不错的作弊......

$in = create_function('$a,$l,$h', 'return $a>=$l && $a<=$h;');
$var = 4;
switch (true) {
  case ($var === 1): echo 1; break;
  case ($var === 2): echo 2; break;
  case $in($var, 3, 5): echo "3..5"; break;
  case $in($var, 6, 10): echo "6..10"; break;
  default: echo "else";
} 

Answer 5

如果您有更复杂的条件，您可以将它们包装在一个函数中。这是一个过于简单的例子：

$chartID = 20;
$somethingElse = true;

switch (switchRanges($chartID, $somethingElse)) {
  case "do this":
      echo "This is done";
      break;
  case "do that":
      echo "that is done";
      break;
  default:
      echo "do something different";
}

function switchRanges($chartID, $somethingElse = false)
{
    if (in_array($chartID, [20, 30]) && $somethingElse === true) {
        return "do this";
    }
    if (in_array($chartID, [20, 50]) && $somethingElse === false) {
        return "do that";
    }
}

Answer 6

我想我会用一种简单的方式来做。

switch($t = 100){
    case ($t > 99 && $t < 101):
        doSomething();
        break;
}