为代码添加注释

要为代码添加良好的注释有时似乎和编写代码一样难。要了解应该为哪些内容添加注释并不容易，因为我们常常倾向于注释代码当前做的事情。注释代码的目的是不错的主意。在函数的不是很明显的头部代码块中，告诉读者方法的输入和输出，以及方法的最初目标。

注释代码当前做什么是很常见的，但这是不必要的。如果代码很复杂，不得不注释它当前在做什么，这将暗示您应该重写代码，让它更容易理解。学会使用良好的名称和更短的方法，在不提供注释说明其用途的情况下提高代码的可读性。

不良习惯：函数注释过多或不足

清单 5 中的注释仅告诉读者代码在做什么 — 它正在通过一个循环进行迭代或添加一个数字。但它忽略了它为什么 做当前的工作。这使维护该代码的人员不知道是否可以安全地更改代码（不引入新缺陷）。

清单 5. 不良习惯：函数注释过多或不足

<?php
class ResultMessage
{
private $severity;
private $message;
public function __construct($sev, $msg)
{
$this->severity = $sev;
$this->message = $msg;
}
public function getSeverity()
{
return $this->severity;
}
public function setSeverity($severity)
{
$this->severity = $severity;
}
public function getMessage()
{
return $this->message;
}
public function setMessage($msg)
{
$this->message = $msg;
}
}
function cntMsgs($messages)
{
$n = 0;
/* iterate through the messages… */
foreach($messages as $m) {
if ($m->getSeverity() == ‘Error’) {
$n++; // add one to the result;
}
}
return $n;
}
$messages = array(new ResultMessage(”Error”, “This is an error!”),
new ResultMessage(”Warning”, “This is a warning!”),
new ResultMessage(”Error”, “This is another error!”));
$errs = cntMsgs($messages);
echo(”There are ” . $errs . ” errors in the result.n”);
?>

良好习惯：带注释的函数和类

清单 6 中的注释告诉读者类和方法的目的。该注释解释了为什么代码在做当前的工作，这对未来维护代码十分有用。可能需要根据条件变更而修改代码，如果能够轻松了解代码的目的，则修改起来很容易。

清单 6. 良好习惯：带注释的函数和类

<?php
/**
* The ResultMessage class holds a message that can be returned
* as a result of a process. The message has a severity and
* message.
*
* @author nagood
*
*/
class ResultMessage
{
private $severity;
private $message;
/**
* Constructor for the ResultMessage that allows you to assign
* severity and message.
* @param $sev See {@link getSeverity()}
* @param $msg
* @return unknown_type
*/
public function __construct($sev, $msg)
{
$this->severity = $sev;
$this->message = $msg;
}
/**
* Returns the severity of the message. Should be one
* “Information”, “Warning”, or “Error”.
* @return string Message severity
*/
public function getSeverity()
{
return $this->severity;
}
/**
* Sets the severity of the message
* @param $severity
* @return void
*/
public function setSeverity($severity)
{
$this->severity = $severity;
}
public function getMessage()
{
return $this->message;
}
public function setMessage($msg)
{
$this->message = $msg;
}
}
/*
* Counts the messages with the given severity in the array
* of messages.
*
* @param $messages An array of ResultMessage
* @return int Count of messages with a severity of “Error”
*/
function countErrors($messages)
{
$matchingCount = 0;
foreach($messages as $m) {
if ($m->getSeverity() == “Error”) {
$matchingCount++;
}
}
return $matchingCount;
}
$messages = array(new ResultMessage(”Error”, “This is an error!”),
new ResultMessage(”Warning”, “This is a warning!”),
new ResultMessage(”Error”, “This is another error!”));
$errs = countErrors($messages);
echo(”There are ” . $errs . ” errors in the result.n”);
?>