代碼寫了5年，必然會(huì)產(chǎn)生審丑疲勞牡肉，代碼混亂不堪捧灰，無(wú)法維護(hù)，可閱讀性基本沒(méi)有统锤。面對(duì)種種的問(wèn)題毛俏，如何使代碼更優(yōu)雅，更具可讀性便成了迫切需要解決的問(wèn)題饲窿。下面我從實(shí)戰(zhàn)中總結(jié)了四項(xiàng)基本原則煌寇，只要你靈活運(yùn)用，我保證你的代碼絕對(duì)漂亮的讓自己不敢相信逾雄。下面我嘗試以一種教學(xué)的方式教給你這四項(xiàng)基本原則阀溶。

一腻脏、把代碼按邏輯相關(guān)性分成不同的段落,亮點(diǎn)是每個(gè)段落可以給個(gè)總結(jié)性的注釋

我們可能都寫過(guò)作文，試想一下银锻，如果一篇文章沒(méi)有任何分段永品，一氣呵成，你閱讀之后會(huì)有什么感想击纬？會(huì)不會(huì)想殺了作者鼎姐？

其實(shí)，碼代碼和寫文章是可以類比的掉弛，如果你寫得代碼中沒(méi)有任何分段症见，對(duì)于代碼閱讀者來(lái)說(shuō)難道不是地獄嗎？可能語(yǔ)言的描述終究是太抽象殃饿，那我就呈上兩個(gè)例子讓大家吐槽一下吧谋作。
示例1：

public interface FrontendServer {
    void viewProfile(HttpRequest request);
    void openDatabase(String location,String user);
    void saveProfile(HttpRequest request);
    String extractQueryParam(HttpRequest request,String param);
    void replyOK(HttpRequest request,String html);
    void findFriends(HttpRequest request);
    void replyNotFound(HttpRequest request,String error);
    void closeDatabase(String location);
}

示例2：

# Import the user's email contracts, and match them to users in our system.
# Then display a list of those users that he/she isn't already friends with.
def suggest_new_friends(user,email_password):
    friends = user.friends()
    friend_emails = set(f.email for f in friends)
    contacts = import_contacts(user.email,email_password)
    contact_emails = set(c.email for c in contacts)
    non_friend_emails = contact_emails-friend_emails
    suggested_friends = User.objects.select(email_in=non_friend_emails)
    display['user'] = user
    display['friends'] = friends
    display['suggested_friends'] = suggested_friends
    return render("suggested_friends.html",display)

吐槽時(shí)間。乎芳。遵蚜。

嘗試使用一下我們的代碼分段原則，閃亮的結(jié)果如下：

示例1應(yīng)用原則一：

public interface FrontendServer {
    // Handlers
    void viewProfile(HttpRequest request);
    void saveProfile(HttpRequest request);
    void findFriends(HttpRequest request);

    // Request/Reply Utilities
    String extractQueryParam(HttpRequest request,String param);
    void replyOK(HttpRequest request,String html);
    void replyNotFound(HttpRequest request,String error);
    
    // Database Helpers
    void openDatabase(String location,String user);
    void closeDatabase(String location);
}

示例2應(yīng)用原則一：

# Import the user's email contracts, and match them to users in our system.
# Then display a list of those users that he/she isn't already friends with.
def suggest_new_friends(user,email_password):
    # Get the user's friends' email addresses.
    friends = user.friends()
    friend_emails = set(f.email for f in friends)

    # Import all email addresses from this user's email account.
    contacts = import_contacts(user.email,email_password)
    contact_emails = set(c.email for c in contacts)

    # Find matching users that  they aren't already friends with.
    non_friend_emails = contact_emails-friend_emails
    suggested_friends = User.objects.select(email_in=non_friend_emails)

    @ Display these lists on the page.
    display['user'] = user
    display['friends'] = friends
    display['suggested_friends'] = suggested_friends
    
    return render("suggested_friends.html",display)

二奈惑、使用一致的布局吭净，讓相似的代碼看起來(lái)相似

你要問(wèn)我為什么讓相似的代碼看起來(lái)相似會(huì)使代碼更清晰更容易理解，我竟然無(wú)言以對(duì)肴甸。自以為可能是人類的認(rèn)知原理導(dǎo)致的寂殉，我無(wú)法給出更官方的解釋，但是我可以給你幾個(gè)例子讓你好好體會(huì)一下如果不這么做帶來(lái)的后果原在。
示例1：

public class PerformanceTester {
    public static final TcpConnectionSimulator wifi = new TcpConnectionSimulator(
            500, /* kpbs */
            80, /* millisecs latency */
            200, /* jitter */
            1 /* packet loss % */);
    public static final TcpConnectionSimulator t3_fiber =
            new TcpConnectionSimulator(
                500, /* kpbs */
                80, /* millisecs latency */
                200, /* jitter */
                1 /* packet loss % */);
    public static final TcpConnectionSimulator cell = new TcpConnectionSimulator(
            100, /* kbps */
            400, /* millisecs latency */
            250, /* jitter */
            5 /* packet loss % */);

}

我們使用原則二來(lái)變化示例1友扰，結(jié)果如下：

public class PerformanceTester {
    public static final TcpConnectionSimulator wifi = 
            new TcpConnectionSimulator(
            500, /* kpbs */
            80,  /* millisecs latency */
            200, /* jitter */
            1    /* packet loss % */);
    public static final TcpConnectionSimulator t3_fiber =
            new TcpConnectionSimulator(
            500, /* kpbs */
            80,  /* millisecs latency */
            200, /* jitter */
            1    /* packet loss % */);
    public static final TcpConnectionSimulator cell = 
            new TcpConnectionSimulator(
            100, /* kbps */
            400, /* millisecs latency */
            250, /* jitter */
            5    /* packet loss % */);

}

變換的結(jié)果很讓人眼前一亮，但還不是很完美庶柿，通過(guò)原則三村怪，會(huì)將完美進(jìn)行到極致。我們首先介紹一下原則三浮庐。

三甚负、使用方法或者其他技術(shù)消除重復(fù)的代碼

消除代碼塊中重復(fù)的代碼，會(huì)使得代碼邏輯更加簡(jiǎn)潔清晰审残，更具表達(dá)性梭域，重點(diǎn)更加突出。
示例1：

public class PerformanceTester {
    public static final TcpConnectionSimulator wifi = 
            new TcpConnectionSimulator(
            500, /* kpbs */
            80,  /* millisecs latency */
            200, /* jitter */
            1    /* packet loss % */);
    public static final TcpConnectionSimulator t3_fiber =
            new TcpConnectionSimulator(
            500, /* kpbs */
            80,  /* millisecs latency */
            200, /* jitter */
            1    /* packet loss % */);
    public static final TcpConnectionSimulator cell = 
            new TcpConnectionSimulator(
            100, /* kbps */
            400, /* millisecs latency */
            250, /* jitter */
            5    /* packet loss % */);

示例1應(yīng)用原則三：

public class PerformanceTester {
    // TcpConnectionSimulator(throughput, latency, jitter, packet_loss)
    //                            [Kbps]   [ms]    [ms]    [percent]   
    
    public static final TcpConnectionSimulator wifi =
            new TcpConnectionSimulator(500, 80, 200, 1);
    public static final TcpConnectionSimulator t3_fiber =
            new TcpConnectionSimulator(500, 80, 200, 1);
    public static final TcpConnectionSimulator cell =
            new TcpConnectionSimulator(100, 400, 250, 5);
}

示例2:

 DatabaseConnectio database_connection;
    string error;
    assert(expandFullName(database_connection,"Doug Adams",&error)=="Mr. Douglas Adams");
    assert(error == "");   
    assert(expandFullName(database_connection,"No Such Guy",&error)=="");
    assert(error =="no match found");   
    assert(expandFullName(database_connection,"John",&error)=="");
    assert(error =="more than one result");

示例2應(yīng)用原則三:

    checkFullName("Doug Adams","Mr. Douglas Adams","");
    checkFullName("Jake Brown","Mr. Jake Brown III","");
    checkFullName("No Such Guy","","no match found");
    checkFullName("John","","more than one result");

    void checkFullName(String partial_name,
                       String expeted_full_name,
                       String expected_error){
        // database_connection is now a class member
        String error;
        String full_name = expandFullName(database_connection,partial_name,&error);
        assert(error == expected_error);
        assert(full_name == expeted_full_name);
    }

四搅轿、使用列對(duì)齊來(lái)使代碼更加易讀

使用列對(duì)齊的方式組織代碼碰辅，可以讓語(yǔ)句之間的對(duì)應(yīng)關(guān)系清晰明顯，閱讀者從中很容易獲取方法的調(diào)用規(guī)則等信息介时，這對(duì)于理解代碼和發(fā)現(xiàn)代碼中的錯(cuò)誤有極大幫助没宾。

示例1：

    checkFullName("Doug Adams","Mr. Douglas Adams","");
    checkFullName("Jake Brown","Mr. Jake Brown III","");
    checkFullName("No Such Guy","","no match found");
    checkFullName("John","","more than one result");

示例1應(yīng)用原則四：

    checkFullName("Doug Adams"  , "Mr. Douglas Adams"  , "");
    checkFullName("Jake Brown"  , "Mr. Jake Brown III" , "");
    checkFullName("No Such Guy" , ""                   , "no match found");
    checkFullName("John"        , ""                   , "more than one result");

示例2：

# Extract POST parameters to local variables
details = request.POST.get('details')
location = request.POST.get('location')
phone = request.POST.get('phone')
email = request.POST.get('email')
url = request.POST.get('url')

示例2應(yīng)用原則四：

# Extract POST parameters to local variables
details  = request.POST.get('details')
location = request.POST.get('location')
phone    = request.POST.get('phone')
email    = request.POST.get('email')
url      = request.POST.get('url')

如果想了解更多信息或者對(duì)開源項(xiàng)目感興,請(qǐng)加我的微信公眾號(hào)凌彬，我在那里等你

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