《模式——工程化实现及扩展》（设计模式C# 版）《迭代器模式 Iterator》——“自我检验" 参考答案

转自：《模式——工程化实现及扩展》（设计模式C# 版）

http://www.cnblogs.com/callwangxiang/

 

 

1、 请遍历当前文件夹列举所有最近3天创建或修改的文件的全路径

 

参考答案

using System;
using System.Diagnostics;
using System.Linq;
using System.IO;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace MarvellousWorks.PracticalPattern.Iterator.Tests.Exercise
{
    [TestClass]
    public class IterateFileFixture
    {
        const string Path = @".";

        [TestMethod]
        public void TestListModifiedAndNewCreatedFiles()
        {
            Func<DateTime, bool> lessThanThreeDaysHandler = x => (DateTime.Now - x).Days <= 3;
            var files =
                new DirectoryInfo(Path).GetFiles().Where(x =>
                                                         lessThanThreeDaysHandler(x.LastWriteTime) ||
                                                         lessThanThreeDaysHandler(x.CreationTime)
                    );

            //  当前单元测试目录下一定会有些新编译的文件
            Assert.IsTrue(files.Count() > 0);

            //  输出匹配信息
            foreach(var file in files)
            {
                Trace.Write(file.FullName);
                if(lessThanThreeDaysHandler(file.LastWriteTime))
                    Trace.Write("\tM");
                if (lessThanThreeDaysHandler(file.CreationTime))
                    Trace.Write("\tC");
                Trace.WriteLine("");
            }
        }
    }
}

 

------ Test started: Assembly: Iterator.Tests.dll ------

E:\MarvelousWorks\unitTest\Iterator.Tests\bin\Debug\Iterator.dll    C
E:\MarvelousWorks\unitTest\Iterator.Tests\bin\Debug\Iterator.pdb    C
E:\MarvelousWorks\unitTest\Iterator.Tests\bin\Debug\Iterator.Tests.dll    M    C
E:\MarvelousWorks\unitTest\Iterator.Tests\bin\Debug\Iterator.Tests.pdb    M    C

1 passed, 0 failed, 0 skipped, took 0.48 seconds (MSTest 10.0).

 

 

2、 请以Attribute方式通过标识不同对象主题，确保迭代器可以根据不同的主题遍历相关内容

 

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace MarvellousWorks.PracticalPattern.Iterator.Tests.Exercise
{
    [TestClass]
    public class AttributSubjectedIteratorFixture
    {
        [Serializable]
        [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
        class IterableAttribute : Attribute{}

        class SubjectAAttribute : IterableAttribute{}
        class SubjectBAttribute : IterableAttribute { }

        static class SubjectedIterator
        {
            /// <summary>
            /// 按照指定的主题——即Attribute遍历
            /// </summary>
            /// <typeparam name="TElement">集合元素类型</typeparam>
            /// <typeparam name="TAttribute">遍历所针对的Attribute类型</typeparam>
            /// <param name="data"></param>
            /// <returns></returns>
            public static IEnumerable<TElement> GetEnumerator<TElement, TAttribute>(IEnumerable<TElement> data)
                where TAttribute : IterableAttribute
            {
                if(data == null) return null;
                if (data.Count() == 0) return data;

                return data.Where(x =>
                                  x.GetType().GetCustomAttributes(typeof (TAttribute), false).Length > 0);
            }
        }


        [SubjectA]
        class A{}

        [SubjectB]
        class B{}

        [SubjectA]
        [SubjectB]
        class AB{}

        class O{}

        [TestMethod]
        public void TestIterateBySubject()
        {
            var data = new List<object> {new A(), new B(), new AB(), new A(), new O {}, new O {}, new AB()};

            var subjectA = SubjectedIterator.GetEnumerator<object, SubjectAAttribute>(data);
            Assert.AreEqual<int>(4, subjectA.Count());      //  两个A两个AB

            var subjectB = SubjectedIterator.GetEnumerator<object, SubjectBAttribute>(data);
            Assert.AreEqual<int>(3, subjectB.Count());      //  1个B两个AB
        }
    }
}