为什么有的人把代码写的如此复杂?

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所属分类:.NET技术
摘要

技术群里有人发了一段代码:附言:兄弟们,这个单例怎么样?我回复:什么鬼,看不懂啊?!

技术群里有人发了一段代码:

为什么有的人把代码写的如此复杂?

附言:兄弟们,这个单例怎么样?

我回复:什么鬼,看不懂啊?!

也有其他小伙伴表示看不懂,看来大家的C#基础和我一样并不全面。

我看不懂,主要是因为我没用过TaskCompletionSource和Interlocked的CompareExchange方法,然后经过我1、2个小时的研究,终于勉强看懂了。

由于上面这段代码只贴了一张图,我没有拿到源码,所以我写了个差不多的Demo用于测试,代码如下:

为什么有的人把代码写的如此复杂?为什么有的人把代码写的如此复杂?

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks;  namespace SingletonTest {     public class Singleton     {         private static Task<string> _stringTask;          /// <summary>         /// 重置,方便重复测试         /// </summary>         public void Reset()         {             _stringTask = null;         }          public Task<string> InitAsync()         {             if (_stringTask != null)             {                 return _stringTask;             }              var inition = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);              var initonTask = Interlocked.CompareExchange(ref _stringTask, inition.Task, null);              if (initonTask != null)             {                 return initonTask;             }              _stringTask = CreateContent(inition);             return inition.Task;         }          private async Task<string> CreateContent(TaskCompletionSource<string> inition)         {             string content = await TextUtil.GetTextAsync();             inition.SetResult(content);             return content;         }     } }

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然后按照我自己的习惯,又写了一版:

为什么有的人把代码写的如此复杂?为什么有的人把代码写的如此复杂?

using System; using System.Collections.Concurrent; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks;  namespace SingletonTest {     class Singleton2     {         private static string _value;         private SemaphoreSlim _semaphoreSlim = new SemaphoreSlim(1, 1);          /// <summary>         /// 重置,方便重复测试         /// </summary>         public void Reset()         {             _value = null;         }          public async Task<string> InitAsync()         {             if (_value != null)             {                 return _value;             }              await _semaphoreSlim.WaitAsync();             if (_value == null)             {                 _value = await TextUtil.GetTextAsync();             }             _semaphoreSlim.Release();              return _value;         }      } }

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很容易懂,不是吗? 

这段代码我好像是理解了,可是我不理解的是,为什么代码会写的这么复杂呢?

最主要的是我不理解下面几行:

为什么有的人把代码写的如此复杂?为什么有的人把代码写的如此复杂?

var inition = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);  var initonTask = Interlocked.CompareExchange(ref _stringTask, inition.Task, null);  if (initonTask != null) {     return initonTask; }

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我要给它翻译成我能理解的代码,我意思到new的TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously)也是个单例,所以我先写了个TaskCompletionSourceFactory类:

为什么有的人把代码写的如此复杂?为什么有的人把代码写的如此复杂?

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks;  namespace SingletonTest {     public class TaskCompletionSourceFactory : IDisposable     {         private TaskCompletionSource<string> _value;          private TaskCompletionSourceData _data;          private SemaphoreSlim _semaphoreSlim = new SemaphoreSlim(1, 1);          public TaskCompletionSourceData Instance         {             get             {                 _semaphoreSlim.Wait();                 if (_value == null)                 {                     _data = new TaskCompletionSourceData();                     _value = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);                     _data.Value = _value;                     _data.First = true;                 }                 else                 {                     _data = new TaskCompletionSourceData();                     _data.Value = _value;                     _data.First = false;                 }                 _semaphoreSlim.Release();                 return _data;             }         }          public void Dispose()         {             _semaphoreSlim.Dispose();         }     }      public class TaskCompletionSourceData     {         public bool First { get; set; }          public TaskCompletionSource<string> Value { get; set; }     } }

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然后把Demo中Singleton这个类改写了一下:

为什么有的人把代码写的如此复杂?为什么有的人把代码写的如此复杂?

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks;  namespace SingletonTest {     public class Singleton3     {         private static Task<string> _stringTask;          /// <summary>         /// 重置,方便重复测试         /// </summary>         public void Reset()         {             _stringTask = null;         }          public Task<string> InitAsync(TaskCompletionSourceFactory factory)         {             if (_stringTask != null)             {                 return _stringTask;             }              var inition = factory.Instance;             if (!inition.First)             {                 return inition.Value.Task;             }              _stringTask = CreateContent(inition.Value);             return inition.Value.Task;         }          private async Task<string> CreateContent(TaskCompletionSource<string> inition)         {             string content = await TextUtil.GetTextAsync();             inition.SetResult(content);             return content;         }     } }

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当我差不多理解了之后,我发现原始代码有一点点小问题,就是TaskCompletionSource<string>是有机率被重复new的。

大家觉得哪种写法好呢?

附:

TextUtil.cs代码,是一个模拟获取文本的方法:

为什么有的人把代码写的如此复杂?为什么有的人把代码写的如此复杂?

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks;  namespace SingletonTest {     public class TextUtil     {         public static Task<string> GetTextAsync()         {             return Task.Run<string>(() =>             {                 Thread.Sleep(10);                 Random rnd = new Random();                 return rnd.Next(0, 1000).ToString().PadRight(10);             });         }     } }

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测试代码:

为什么有的人把代码写的如此复杂?为什么有的人把代码写的如此复杂?

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks;  namespace SingletonTest {     class Program     {         private static int _count = 200;         private static Singleton _singleton = new Singleton();         private static Singleton2 _singleton2 = new Singleton2();         private static Singleton3 _singleton3 = new Singleton3();          static void Main(string[] args)         {             ThreadPool.SetMinThreads(20, 20);             Task.Run(() => { }); //Task预热             Console.WriteLine("输入1测试Singleton,输入2测试Singleton2,如果值都相同,说明单例测试通过,否则不通过");              while (true)             {                 var key = Console.ReadKey().Key;                  if (key == ConsoleKey.D1)                 {                     Console.WriteLine("测试Singleton");                     Test();                 }                  if (key == ConsoleKey.D2)                 {                     Console.WriteLine("测试Singleton2");                     Test2();                 }                  if (key == ConsoleKey.D3)                 {                     Console.WriteLine("测试Singleton3");                     Test3();                 }             }          }          public static void Test()         {             List<Task> taskList = new List<Task>();             for (int i = 0; i < _count; i++)             {                 Task task = Task.Run(async () =>                 {                     string content = await _singleton.InitAsync();                     Console.Write(content);                 });                 taskList.Add(task);             }              Task.WaitAll(taskList.ToArray());             _singleton.Reset();             Console.WriteLine("");         }          public static void Test2()         {             List<Task> taskList = new List<Task>();             for (int i = 0; i < _count; i++)             {                 Task task = Task.Run(async () =>                 {                     string content = await _singleton2.InitAsync();                     Console.Write(content);                 });                 taskList.Add(task);             }              Task.WaitAll(taskList.ToArray());             _singleton2.Reset();             Console.WriteLine("");         }          public static void Test3()         {             TaskCompletionSourceFactory factory = new TaskCompletionSourceFactory();             List<Task> taskList = new List<Task>();             for (int i = 0; i < _count; i++)             {                 Task task = Task.Run(async () =>                 {                     string content = await _singleton3.InitAsync(factory);                     Console.Write(content);                 });                 taskList.Add(task);             }              Task.WaitAll(taskList.ToArray());             _singleton3.Reset();             factory.Dispose();             Console.WriteLine("");         }     } }

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