If—Else \ If-ElseIf—Else 的随想、改造

最新推荐文章于 2025-03-18 11:35:36 发布

转载最新推荐文章于 2025-03-18 11:35:36 发布 · 86 阅读

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原文链接：http://www.cnblogs.com/RuiLei/archive/2010/08/27/1809883.html

本文探讨了使用Command模式来替代传统的If-Else及If-ElseIf-Else语句的方法，通过创建一系列Command对象来简化复杂的条件判断逻辑，并展示了不同应用场景下的实现方式。

最近有一个想法，想把这些If--Else、If-ElseIf-Else，全部换成一条条的Command,然后把这个Command串起来，最后放到CommandList中把它们一锅端了。:)

所以以下就这个想法产物：

先列举一下通常的分支、支叉

static String IfElseIfElse (Int32 conditionParam) {
            var result = String.Empty;
            if ( conditionParam == 1 ) {
                result = "conditionParam1";
            }
            else if ( conditionParam == 2 ) {
                result = "conditionParam2";
            }
            else {
                result = "default";
            }
            return result;
        }

那现在就按照想法、分不同场景来进化Code吧

场景1：根据传统的If-Else进行的改造，只适用传统的True Or Else的操作

声明方法： T ExecuteCommand<T> (IDictionary<Boolean , List<Func<T>>> commandList)

具体代码：

          /// <summary>
       /// 适用传统的True Or False的操作
       /// </summary>
       static T ExecuteCommand<T> (IDictionary<Boolean , List<Func<T>>> commandList) {
           T t = default ( T );
           foreach ( var command in commandList ) {
               if ( command.Key ) {
                   t = command.Value[0] ();
                   break;
               }
               else {
                   t = command.Value[1] ();
                   break;
               }
           }
           return t;
       }

具体应用：

            /// <summary>
      /// 根据传统的If-Else进行的改造
      /// </summary>
      static String CommandList (Int32 conditionParam) {

--------------------------------------------------------------------------------------------------------------------------------------------------

场景2：根据“场景1”缺点，增加了对If-ElseIf-Else的支持

声明方法： T ExecuteCommand<T> (Boolean? condition , Func<T> action)

具体代码：

          /// <summary>
       /// 适用True And False And Default的操作
       /// </summary>
       static T ExecuteCommand<T> (Boolean? condition , Func<T> action) {
           T t = default ( T );
           if ( condition.HasValue ) {
               if ( condition.Value ) { t = action (); }
           }
           else {
               t = action ();
           }
           return t;
       }

具体应用：

             /// <summary>
       /// 增加了对If-ElseIf-Else的支持
       /// </summary>
       static String CommandFuncList (Int32 conditionParam) {
           var commandList = new List<String> (){
            ExecuteCommand<String>(( conditionParam ==1 ),
                                   ()=> { return "conditionParam1"; }
            ),
            ExecuteCommand<String>(( conditionParam ==2 ),
                                   ()=> { return "conditionParam2"; }
            ),
            ExecuteCommand<String>(null,
                                   ()=> { return "default"; }
            )
           };
           return commandList.Where ( o => o != null ).First ();
       }

--------------------------------------------------------------------------------------------------------------------------------------------------

以上场景都是带返回值，那如何对不同分支、不同那个什么；只想执行方法，一个方法或多个方法，又应该如何处理呢？

场景3：告诉我们还可以这样干

声明方法：List<Action> ExecuteCommand (Boolean? condition , List<Action> action)

具体方法：

             /// <summary>
       /// 只适用If-Else的方法操作
       /// </summary>
       static List<Action> ExecuteCommand (Boolean? condition , List<Action> action) {
           List<Action> _action = default ( List<Action> );
           if ( condition.HasValue ) {
               if ( condition.Value ) {
                   _action = action;
               }
           }
           else {
               _action = action;
           }
           return _action;
       }

具体应用：

     static void CommandActionList (Int32 conditionParam) {
            var commandList = new List<List<Action>> (){
             ExecuteCommand(( conditionParam ==1 ),
                            new List<Action>() { ()=> Write() }
             ),
             ExecuteCommand(( conditionParam ==2 ),
                            new List<Action>(){
                                  ()=> Write(),
                                  ()=> WriteAction()
                            }
             )
            };
            commandList.Where ( o => o != null ).Select ( o => o ).ToList ().ForEach ( o => o.ForEach ( i => i () ) );
        }

--------------------------------------------------------------------------------------------------------------------------------------------------

场景4：告诉我们，加上执行步骤，会让我们对分支掌控游刃有余

声明方法：List<Action> ExecuteCommand (ref Boolean execStep , Boolean? condition , List<Action> action)

具体方法：

        static List<Action> ExecuteCommand (ref Boolean execStep , Boolean? condition , List<Action> action) {
            List<Action> _action = default ( List<Action> );
            if ( execStep ) {
                if ( condition.HasValue ) {
                    if ( condition.Value ) {
                        _action = action;
                        execStep = false;
                    }

                }
                else {
                    _action = action;
                    execStep = false;
                }
            }
            return _action;
        }

具体应用：

       static void CommandActionListWithStep (Int32 conditionParam) {
            var execStep = true;
            var commandList = new List<List<Action>> (){
             ExecuteCommand(ref execStep,( conditionParam ==1 ),
                            new List<Action>() { ()=> Write() }
             ),
             ExecuteCommand(ref execStep,( conditionParam ==2 ),
                            new List<Action>(){
                                  ()=> Write(),
                                  ()=> WriteAction()
                            }
             ),
             ExecuteCommand(ref execStep,null, new List<Action>(){ ()=> WriteDefault() } )
            };

            commandList.FindAll ( (p) => { return p != null; } )
                       .ForEach ( o => o.ForEach ( i => i () ) );
        }

static void Write () { Console.Write ( "Hello Command" ); }

static void WriteAction () { Console.Write ( "Hello Action" ); }

static void WriteDefault () { Console.Write ( "Hello Default" ); }

--------------------------------------------------------------------------------------------------------------------------------------------------

最终全部方法执行结果：

static void Main (string[] args) {
           Console.Write ( "IfElseIfElse ( 1 )" + IfElseIfElse ( 1 ) );
           Console.WriteLine ();
           Console.Write ( "IfElseIfElse ( 4 )" + IfElseIfElse ( 4 ) );
           Console.WriteLine ();
           Console.Write ( "CommandList ( 1 )" + CommandList ( 1 ) );
           Console.WriteLine ();
           Console.Write ( "CommandList ( 2 )" + CommandList ( 2 ) );
           Console.WriteLine ();
           Console.Write ( "CommandFuncList ( 1 )" + CommandFuncList ( 1 ) );
           Console.WriteLine ();
           Console.Write ( "CommandFuncList ( 4 )" + CommandFuncList ( 4 ) );
           Console.WriteLine ();
           CommandActionList ( 1 );
           Console.WriteLine ();
           CommandActionList ( 2 );
           Console.WriteLine ();
           CommandActionListWithStep ( 1 );
           Console.WriteLine ();
           CommandActionListWithStep ( 4 );
           Console.WriteLine ();
       }

转载于:https://www.cnblogs.com/RuiLei/archive/2010/08/27/1809883.html