设计模式01-SOLID(S)单一职责原则

Single Responsibility Principle:单一职责原则

• Single: 单一功能，各个部分保持独立，避免一个程序负责大于等于两个以上的功能

•          public class Log
           {
               private readonly List<string> entries = new List<string>();
               private static int count = 0;
               public int AddEntry(string text)
               {
                   entries.Add($"{ count}:{text} ");
                   return count;
               }
               public void RemoveEntry(int index)
               {
                   entries.RemoveAt(index);
               }
               public override string ToString()
               {
                   return String.Join(Environment.NewLine, entries);
               }
           }
  
           public class Persistence
           {
               public void SaveFile(Log log, string fileName, bool overrWrite = false)
               {
                   if (overrWrite||!File.Exists(fileName))
                   {
                       File.WriteAllText(fileName, log.ToString());
                   }
               }
           }
           internal class Program
           {
               static void Main(string[] args)
               {
                   Log log = new Log();
                   log.AddEntry("今天星期三，游玩西湖");
                   log.AddEntry("约球吗？");
                   Persistence persistence = new Persistence();
                   string fileName = @"..\DesignPartterns\log.txt";
                   persistence.SaveFile(log, fileName, true);
                   var p = new Process();
                   p.StartInfo = new ProcessStartInfo(fileName)
                   {
                       UseShellExecute = true
                   };
                   p.Start();
               }
           }