有些人問,優(yōu)秀程序員和大牛有什么區(qū)別,大概有10到20種吧。因為大牛有很好的編程習慣和豐富的經(jīng)驗,所以他們非常的高效。如果不好的編程習慣出現(xiàn)在你的代碼里,你的代碼效率就會降低。本文闡述一些好的編程習慣,他們可以讓你成為更好的程序員。

這些習慣能讓你的代碼在高效運行的同時提高可維護性。你寫代碼的時候,可能大部分時間都浪費在維護上了,程序的維護代價很高。培養(yǎng)良好的編程習慣,如模塊化設計,可以讓你的代碼可讀性更好,從而容易維護。

代碼中的問題往往伴隨著不良的編程習慣,而且后者會導致代碼不好修改并可能出現(xiàn)新的缺陷。下面有五個好的編程習慣,將幫你避免這些陷阱:

使用友好的命名方式。

使用更精悍短小的代碼。

注釋你的代碼。

編寫異常處理。

永遠,永遠不要復制粘貼.

下面的章節(jié)將解釋這些習慣。

良好的命名方式是最重要的編程習慣,因為好的命名會讓代碼易懂,好懂。代碼的可讀性決定它的可維護性。即使你在代碼沒有寫注釋,如果它可讀性好的話,它也修改起來也會簡單。你應該在練習開時就使用良好的命名方式,讓你的代碼像一本書一樣。

例1包含一個過短的變量名,寫出這樣的代碼非常不好弄懂,而且函數(shù)名也沒有清晰的描述出這個方法是做什么的。函數(shù)名表示了函數(shù)的功能,如果它卻是做別的用途的,那就會誤導別人。

<?php

function getNBDay($d)

{

switch($d) {

case 5:

case 6:

case 7:

return 1;

default:

return ($d + 1);

}

}

$day = 5;

$nextDay = getNBDay($day);

echo ("Next day is: " . $nextDay . " ");

?>

例2則給出了使用良好命名方式的代碼。重新命名函數(shù)是為了更好的反映它們的功能。變量也重新命名為描述性的。只有一個在循環(huán)中的$i還使用短的變量名。盡管有些人不同意,短變量名在循環(huán)中是請允許的——甚至更好些,因為它們清晰的起到了指針的功能。

<?php

define ('MONDAY', 1);

define ('TUESDAY', 2);

define ('WEDNESDAY', 3);

define ('THURSDAY', 4);

define ('FRIDAY', 5);

define ('SATURDAY', 6);

define ('SUNDAY', 7);

/*

*

* @param $dayOfWeek

* @return int Day of week, with 1 being Monday and so on.

*/

function findNextBusinessDay($dayOfWeek)

{

$nextBusinessDay = $dayOfWeek;

switch($dayOfWeek) {

case FRIDAY:

case SATURDAY:

case SUNDAY:

$nextBusinessDay = MONDAY;

break;

default:

$nextBusinessDay += 1;

break;

}

return $nextBusinessDay;

}

$day = FRIDAY;

$nextBusDay = findNextBusinessDay($day);

echo ("Next day is:" . $nextBusDay . " ");

我鼓勵你在函數(shù)中分隔長的條件給函數(shù)命名,以便于描述這個條件。(玉米:這句話啥意思? 5555)這個技巧會讓你的代碼容易閱讀和擴展,因此它可以被抽象復用。如果條件發(fā)生了改變,這樣也會很容易更新函數(shù).由于方法有一個見名知義的名字,化碼就不會失去它本來的意思或者變得難以理解。

使用更少的代碼

編寫代碼、解決問題是一種容易的事情。當你解決一個正在發(fā)生的問題,編呀編,寫呀寫,你的方法越來越長。只要你回頭使用更少的代碼來重構,就是過了很久也沒什么問題。

重構是個好主意,但你應該養(yǎng)成第一次就寫出更短小精悍代碼的習慣。在一個窗口上(玉米:不用翻頁)就能看全的短小函數(shù)更容易理解。要是一個函數(shù)長出了窗口,就很難理解了,因為你不能快速的從頭到腳的瀏覽整個代碼。

當構思一個方法的時候,你還應該養(yǎng)成一個讓它們只做一件事情的習慣。以下因素寫代碼時應常注意。第一,只做一件事情的函數(shù)更易于復用。第二,這樣的函數(shù)測試更方便。第三,這樣的函數(shù)好讀易懂方便改——如果必要的話——讓它們盡可能的簡單吧。

壞習慣:過長的函數(shù)(很多時候)

例三是過長函數(shù)的表現(xiàn)。它不知道自己要做什么。它做太多的事情,所以沒有集成化。它更難以理解,不好Debug和測試。它遍歷文件建立列表,它給對象賦值,它做一些計算,……它耕田,它澆水,甚至做更多事情。(^_^)

例三. 壞習慣:過長函數(shù)

<?php

function writeRssFeed($user)

{

// get the DB connection information

// look up the user's preferences...

$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password')

OR die(mysql_error());

// Query

$perfsQuery = sprintf("SELECT max_stories FROM user_perfs WHERE user= '%s'", mysql_real_escape_string($user));

$result = mysql_query($query, $link);

$max_stories = 25; // default it to 25;

if ($row = mysql_fetch_assoc($result)) {

$max_stories = $row['max_stories'];

}

// go get my data

$perfsQuery = sprintf("SELECT * FROM stories WHERE post_Date = '%s'", mysql_real_escape_string());

$result = mysql_query($query, $link);

$feed = "<rss version="2.0">" .

"<channel>" .

"<title>My Great Feed</title>" .

"<link>;/link>" .

"<description>The best feed in the world</description>" .

"<language>en-us</language>" .

"<pubDate>Tue, 20 Oct 2008 10:00:00 GMT</pubDate>" .

"<lastBuildDate>Tue, 20 Oct 2008 10:00:00 GMT</lastBuildDate>" .

"<docs>;/docs>" .

"<generator>MyFeed Generator</generator>" .

"<managingEditor>[email protected]</managingEditor>" .

"<webMaster>[email protected]</webMaster>" .

"<ttl>5</ttl>";

// build the feed...

while ($row = mysql_fetch_assoc($result)) {

$title = $row['title'];

$link = $row['link'];

$description = $row['description'];

$date = $row['date'];

$guid = $row['guid'];

$feed .= "<item>";

$feed .= "<title>" . $title . "</title>";

$feed .= "<link>" . $link . "</link>";

$feed .= "<description> " . $description . "</description>";

$feed .= "<pubDate>" . $date . "</pubDate>";

$feed .= "<guid>" . $guid . "</guid>";

$feed .= "</item>";

}

$feed .= "</rss";

// write the feed out to the server...

echo($feed);

}

?>

要是你再加更多東西到這個函數(shù)里,它會很快變得難以維護。

好習慣:可管理,集成化的函數(shù)

<?php

function createRssHeader()

{

return "<rss version="2.0">" .

"<channel>" .

"<title>My Great Feed</title>" .

"<link>;/link>" .

"<description>The best feed in the world</description>" .

"<language>en-us</language>" .

"<pubDate>Tue, 20 Oct 2008 10:00:00 GMT</pubDate>" .

"<lastBuildDate>Tue, 20 Oct 2008 10:00:00 GMT</lastBuildDate>" .

"<docs>;/docs>" .

"<generator>MyFeed Generator</generator>" .

"<managingEditor>[email protected]</managingEditor>" .

"<webMaster>[email protected]</webMaster>" .

"<ttl>5</ttl>";

}

function createRssFooter()

{

return "</channel></rss>";

}

function createRssItem($title, $link, $desc, $date, $guid)

{

$item .= "<item>";

$item .= "<title>" . $title . "</title>";

$item .= "<link>" . $link . "</link>";

$item .= "<description> " . $description . "</description>";

$item .= "<pubDate>" . $date . "</pubDate>";

$item .= "<guid>" . $guid . "</guid>";

$item .= "</item>";

return $item;

}

function getUsermaxStories($db_link, $default)

{

$perfsQuery = sprintf("SELECT max_stories FROM user_perfs WHERE user= '%s'", mysql_real_escape_string($user));

$result = mysql_query($perfsQuery, $db_link);

$max_stories = $default;

if ($row = mysql_fetch_assoc($result)) {

$max_stories = $row['max_stories'];

}

return $max_stories;

}

function writeRssFeed($user)

{

// get the DB connection information

$settings = parse_ini_file("rss_server.ini");

// look up the user's preferences...

$link = mysql_connect($settings['db_host'], $settings['user'],

$settings['password']) OR die(mysql_error());

$max_stories = getUserMaxStories($link, 25);

// go get my data

$newsQuery = sprintf("SELECT * FROM stories WHERE post_Date = '%s'", mysql_real_escape_string(time()));

$result = mysql_query($newsQuery, $link);

$feed = createRssHeader();

$i = 0;

// build the feed...

while ($row = mysql_fetch_assoc($result)) {

if ($i < $max_stories) {

$title = $row['title'];

$link = $row['link'];

$description = $row['description'];

$Date = $row['Date'];

$guid = $row['guid'];

$feed .= createRssItem($title, $link, $description, $date, $guid);

$i++;

} else {

break;

}

}

mysql_close($link);

$feed .= createRssFooter();

// write the feed out to the server...

echo($feed);

}

?>

把長函數(shù)分割會導致效率降低,所以要注意,這個好習慣不要使用過度。這樣做可能也會引起閱讀性差,跟原來人家是一個整體時沒什么區(qū)別。

注釋代碼

注釋你的代碼有時就像你剛著手寫代碼一樣困難。明確注釋內(nèi)容很棘手,因為他要寫出代碼要做什么。注釋變量是一個好主意。在函數(shù)頭部注釋可能不太明顯時,就可以告訴閱讀者函數(shù)要什么參數(shù),有什么返回以及主要的意圖。

通常大家會注釋代碼是做什么的,但這并不必要。如果代碼讓人困惑以至于你不得不寫注釋說它是做什么的,這就提示你應該重寫它,使它更好懂。命名良好、更加短小、組織合理的代碼習慣會讓你的代碼用不著注釋就擁有很高的可讀性。

壞習慣:壓根沒有或者嘰嘰歪歪的函數(shù)注釋(^_^)

例5的注釋只給出了代碼在做什么——它的通過循環(huán)的遍歷、加了個數(shù)。但是丟了為什么這么做和要做什么。這會讓別人難以不影響原代碼的情形下安全修改的做出修改。

例5 :壓根沒胡或者嘰嘰歪歪的函數(shù)注釋

<?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. ");

?>

好習慣:注釋函數(shù)和類

例6里的注釋標明了類和函數(shù)的意圖。注釋表明方法做了什么和為什么做,這會對將來了解代碼的意圖很有幫助。環(huán)境的變化會需要你進行代碼修改,這就會讓很容易的知道開始時你代碼是做什么的。

例6.好習慣:注釋函數(shù)和類

<?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 meswww.shanxiwang.netsage.

* @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. ");

?>

異常處理

寫健壯應用時經(jīng)常會提到的異常處理,一般遵循著80/20原則:80%的代碼用于處理異?；蛘唑炞C,20%的代碼沒什么實際的用途。原始的代碼通常都是在樂觀的環(huán)境下編寫的。這意味著代碼可以在數(shù)據(jù)正常、一切理解的基礎環(huán)境中工作的很好。但是這種代碼在其生命周期內(nèi)是脆弱的。在極端的情形中,你得花更多的時間來未很可能永遠不會發(fā)生的狀況編寫相應代碼。

這個習慣就是要你處理全部的出錯情況,而且如果要是不這么做,你的代碼永遠也完不成。壞習慣:不處理任何異常

<?php

// get the actual name of the

function convertDayOfWeekToName($day)

{

$dayNames = array(

"Sunday",

"Monday",

"Tuesday",

"Wednesday",

"Thursday",

"Friday",

"Saturday");

return $dayNames[$day];

}

echo("The name of the 0 day is: " . convertDayOfWeekToName(0) . " ");

echo("The name of the 10 day is: " . convertDayOfWeekToName(10) . " ");

echo("The name of the 'orange' day is: " . convertDayOfWeekToName('orange') . " ");

?>

好習慣:防守型編程

例8表明處理并拋出異常是一件很有意義的事情。不只是額外的異常處理可以讓代碼健壯,但是這有助于提高代碼的可讀性。這種異常處理為原作者查看何時編寫提供了一個很好的說明。

例8.好習慣:防守型編程

<?php

/**

* This is the exception thrown if the day of the week is invalid.

* @author nagood

*

*/

class InvalidDayOfWeekException extends Exception { }

class InvalidDayFormatException extends Exception { }

/**

* gets the name of the day given the day in the week. Will

* return an error if the value supplied is out of range.

*

* @param $day

* @return unknown_type

*/

function convertDayOfWeekToName($day)

{

if (! is_numeric($day)) {

throw new InvalidDayFormatException('The value '' . $day . '' is an ' .

'invalid format for a day of week.');

}

if (($day > 6) || ($day < 0)) {

throw new InvalidDayOfWeekException('The day number '' . $day . '' is an ' .

'invalid day of the week. Expecting 0-6.');

}

$dayNames = array(

"Sunday",

"Monday",

"Tuesday",

"Wednesday",

"Thursday",

"Friday",

"Saturday");

return $dayNames[$day];

}

echo("The name of the 0 day is: " . convertDayOfWeekToName(0) . " ");

try {

echo("The name of the 10 day is: " . convertDayOfWeekToName(10) . " ");

} catch (InvalidDayOfWeekException $e) {

echo ("Encountered error while trying to convert value: " . $e->getMessage() . " ");

}

try {

echo("The name of the 'orange' day is: " . convertDayOfWeekToName('orange') . " ");

} catch (InvalidDayFormatException $e) {

echo ("Encountered error while trying to convert value: " . $e->getMessage() . " ");

}

?>

通過檢驗參數(shù)的全法性——這有助于他人使用你需要正確參數(shù)的函數(shù)——你應該檢驗它們

并拋出異常的大意:

盡量拋出接近錯誤的異常.

處理每個特殊的異常.

永遠,永遠不要復制粘貼

把代碼復制到你的編輯里的能力是一把雙刃劍。一方面,它避免了你參照一些示例后重新再打一遍時出現(xiàn)的錯誤;另一方面,它讓書寫相似代碼太簡單了。

你要避免在你的程序應用中復制粘貼代碼。當你發(fā)現(xiàn)自己在這樣做時,停下來并問自己可不可以把復制的部分重復使用。把相同的代碼放在同一個地方可以讓你以后修改時更加的輕松,因為要改變都在一起。

壞習慣:相似的代碼塊

例9表現(xiàn)了除了一些值所在位置之外很相近的幾個方法。有些工具可以檢驗你的代碼中復制粘貼的部分(去看看Resources)。

例9.相似的代碼塊

<?php

/**

* Counts the number of Messages found in the array of

* ResultMessage with the getSeverity() value of "Error"

*

* @param $messages An array of ResultMessage

* @return unknown_type

*/

function countErrors($messages)

{

$matchingCount = 0;

foreach($messages as $m) {

if ($m->getSeverity() == "Error") {

$matchingCount++;

}

}

return $matchingCount;

}

/**

* Counts the number of messages found in the array of

* ResultMessage with the getSeverity() value of "Warning"

*

* @param $messages An array of ResultMessage

* @return unknown_type

*/

function countWarnings($messages)

{

$matchingCount = 0;

foreach($messages as $m) {

if ($m->getSeverity() == "Warning") {

$matchingCount++;

}

}

return $matchingCount;

}

/**

* Counts the number of Messages found in the array of

* ResultMessage with the getSeverity() value of "Information"

*

* @param $messages An array of ResultMessage

* @return unknown_type

*/

function countInformation($messages)

{

$matchingCount = 0;

foreach($messages as $m) {

if ($m->getSeverity() == "Information") {

$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. ");

?>

好習慣:可復用的帶參函數(shù)

例10展示了把要復制的代碼入到一個方法中的代碼修改。另一個修改的方法則把工作代理給了一個新的方法。編寫一個通用的方法要花一些時間來設計,當然這會讓你停下來思考,而不是用復制粘貼的組合快捷鍵。但是這樣做會在以后修改時省回第一次多花的時間。

例10.好習慣:可利用的帶參函數(shù)

<?php

/*

* Counts the messages with the given severity in the array

* of messages.

*

* @param $Messages An array of ResultMessage

* @return int Count of messages matching $withSeverity */

function countMessages($messages, $withSeverity)

{

$matchingCount = 0;

foreach($messages as $m) {

if ($m->getSeverity() == $withSeverity) {

$matchingCount++;

}

}

return $matchingCount;

}

/**

* Counts the number of messages found in the array of

* ResultMessage with the getSeverity() value of "Error"

*

* @param $messages An array of ResultMessage

* @return unknown_type

*/

function countErrors($messages)

{

return countMessages($messages, "Errors");

}

/**

* Counts the number of messages found in the array of

* ResultMessage with the getSeverity() value of "Warning" *

* @param $messages An array of ResultMessage

* @return unknown_type

*/

function countWarnings($messages)

{

return countMessages($messages, "Warning");

}

/**

* Counts the number of messages found in the array of

* ResultMessage with the getSeverity() value of "Warning" *

* @param $messages An array of ResultMessage

* @return unknown_type

*/

function countInformation($Messages)

{

return countMessages($messages, "Information");

}

$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. ");

?>

結(jié)論

如果當你開發(fā)PHP的時候養(yǎng)成了本文中提到的好習慣,你寫的代碼將會好讀、好懂、好維護。編寫可維護代碼的方式將讓你的代碼可以高度排錯,并告別低級錯誤。

使用良好命名并用短代碼塊來組強你的代碼會讓你的代碼簡單明了。注明你代碼的目的會讓它的主旨明確易于理解。異常處理讓你的代碼健壯。最后,摒棄復制粘貼的惡習讓你的代碼整潔。