《編寫可讀程式碼的藝術》第4章審美

阿新 • • 發佈：2020-12-31

1. 為什麼審美這麼重要？

讓人愉悅的程式碼更易讀，因此更容易使用。

2. 重新安排換行來保持一致和緊湊

下面的程式碼有著優雅一致的風格，並且很容易從頭看到尾快速瀏覽。

但是缺憾在於用了更多的縱向空間，並且註釋重複了三遍。

 1 public class PerformanceTester {
 2     public static final TcpConnectionSimulator wifi =
 3         new TcpConnectionSimulator(
 4             500,   /* Kbps */
 5             80,    /* 
 millisecs latency */
 6             200,   /* jitter */
 7             1      /* packet loss % */);
 8             
 9     public static final TcpConnectionSimulator t3_fiber =
10         new TcpConnectionSimulator(
11             45000, /* Kbps */
12             10,    /* millisecs latency */
13             0,     /* 
 jitter */
14             0      /* packet loss % */);
15             
16     public static final TcpConnectionSimulator cell =
17         new TcpConnectionSimulator(
18             100,   /* Kbps */
19             400,   /* millisecs latency */
20             250,   /* jitter */
21             5      /* packet loss %  
*/);
22 }

更緊湊的書寫方式如下：

 1 public class PerformanceTester {
 2     // TcpConnectionSimulator(throughput, latency, jitter, packet_loss)
 3     //                        [Kbps]        [ms]    [ms]    [percent]
 4     public static final TcpConnectionSimulator wifi =
 5         new TcpConnectionSimulator(500, 80, 200, 1);
 6     public static final TcpConnectionSimulator t3_fiber =
 7         new TcpConnectionSimulator(45000, 10, 0, 0);
 8     public static final TcpConnectionSimulator cell =
 9         new TcpConnectionSimulator(100, 400, 250, 5);
10 }

3. 用方法（函式）整理不規則的東西

下面這段程式碼沒有什麼美感可言。

 1 DatabaseConnection database_connection;
 2 string error;
 3 assert(ExpandFullName(database_connection, "Doug Adams", &error)
 4     == "Mr. Douglas Adams");
 5 assert(error == "");
 6 assert(ExpandFullName(database_connection, " Jake Brown ", &error)
 7     == "Mr. Jacob Brown III");
 8 assert(error == "");
 9 assert(ExpandFullName(database_connection, "No Such Guy", &error) == "");
10 assert(error == "no match found");
11 assert(ExpandFullName(database_connection, "John", &error) == "");
12 assert(error == "more than one result");

需要一個輔助函式來改進。

 1 void CheckFullName(string partial_name,
 2                    string expected_full_name,
 3                    string expected_error) {
 4     // database_connection is now a class member
 5     string error;
 6     string full_name = ExpandFullName(database_connection, partial_name, &error);
 7     assert(error == expected_error);
 8     assert(full_name == expected_full_name);
 9 }
10 
11 CheckFullName("Doug Adams", "Mr. Douglas Adams", "");
12 CheckFullName(" Jake Brown ", "Mr. Jake Brown III", "");
13 CheckFullName("No Such Guy", "", "no match found");
14 CheckFullName("John", "", "more than one result");