using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Geovin.Du.DuLazyLoad.DuGhosts { /// <summary> /// Lazy Load Pattern /// </summary> public enum LoadStatus { /// <summary> /// 无加载 /// </summary> Unloaded, /// <summary> /// 正加哉 /// </summary> Loading, /// <summary> /// 已加载 /// </summary> Loaded, } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Geovin.Du.DuLazyLoad.DuGhosts { /// <summary> /// Lazy Load Pattern /// </summary> public class GhostCollege : DomainObject { private string? _missionStatement; private int? _numberOfStudents; private Library? _library; /// <summary> /// /// </summary> /// <param name="id"></param> public GhostCollege(int id) : base(id) { Id = id; Console.WriteLine("学院初始化完成."); } /// <summary> /// /// </summary> public string MissionStatement { get { LoadIfNecessary(); return _missionStatement!; } set => _missionStatement = value; } /// <summary> /// /// </summary> public int NumberOfStudents { get { LoadIfNecessary(); return _numberOfStudents!.Value; } set => _numberOfStudents = value; } /// <summary> /// /// </summary> public Library Library { get { LoadIfNecessary(); return _library!; } set => _library = value; } /// <summary> /// /// </summary> public void ShowDetails() => Console.WriteLine( $"大学的使命是: '{MissionStatement}'.\n" + $"这所学院图书馆拥有藏书 {Library.NumberOfBooks} 册, " + $"成立于 {Library.EstablishmentDate.ToShortDateString()}."); /// <summary> /// /// </summary> /// <returns></returns> protected override object[] FetchData() => new object[3] { "学习、发现、治愈、创造,让世界变得更美好", 850, new Library(), }; /// <summary> /// /// </summary> /// <param name="dataRow"></param> protected override void ApplyLoadedData(object[] dataRow) { Console.WriteLine("数据加载中..."); _missionStatement = (string)dataRow[0]; _numberOfStudents = (int)dataRow[1]; _library = (Library)dataRow[2]; } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Geovin.Du.DuLazyLoad.DuGhosts { /// <summary> /// Lazy Load Pattern /// </summary> public abstract class DomainObject { private LoadStatus _status; /// <summary> /// /// </summary> /// <param name="id"></param> protected DomainObject(int id) { Id = id; } public int Id { get; init; } public bool IsGhost => _status == LoadStatus.Unloaded; public bool IsLoaded => _status == LoadStatus.Loaded; /// <summary> /// Note template method pattern. /// </summary> public virtual void LoadIfNecessary() { if (!IsGhost) { return; } var dataRow = FetchData(); MarkAsLoading(); ApplyLoadedData(dataRow); MarkAsLoaded(); } /// <summary> /// /// </summary> /// <returns></returns> protected abstract object[] FetchData(); /// <summary> /// /// </summary> /// <param name="dataRow"></param> protected abstract void ApplyLoadedData(object[] dataRow); /// <summary> /// /// </summary> private void MarkAsLoading() => _status = LoadStatus.Loading; /// <summary> /// /// </summary> private void MarkAsLoaded() => _status = LoadStatus.Loaded; } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Geovin.Du.DuLazyLoad.DuGhosts { /// <summary> /// Lazy Load Pattern /// </summary> public class CollegeFactory { /// <summary> /// /// </summary> /// <param name="id"></param> /// <returns></returns> public GhostCollege CreateFromId(int id) => new(id); } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using Geovin.Du.BuildingBlocks; namespace Geovin.Du.DuLazyLoad.DuGhosts { /// <summary> /// Lazy Load Pattern /// </summary> public static class GhostsExecutor { /// <summary> /// /// </summary> public static void Execute() { ConsoleExtension.WriteSeparator("Lazy Load Pattern:Ghosts demo"); var collegeFactory = new CollegeFactory(); var college = collegeFactory.CreateFromId(1); // College library shouldn't have been constructed before calling ShowDetails method. Console.WriteLine("给我更多关于这所大学的细节!"); college.ShowDetails(); Console.WriteLine("\n给我更多关于这所大学的细节!"); college.ShowDetails(); } } }
调用:
Geovin.Du.DuLazyLoad.DuGhosts.GhostsExecutor.Execute();
输出:
Lazy Load Pattern:Ghosts demo -------------------------------------------------- 学院初始化完成. 给我更多关于这所大学的细节! 加载库... 数据加载中... 大学的使命是: '学习、发现、治愈、创造,让世界变得更美好'. 这所学院图书馆拥有藏210000册 ,成立于 2008/5/28. 给我更多关于这所大学的细节! 大学的使命是: '学习、发现、治愈、创造,让世界变得更美好'. 这所学院拥有图书馆210000 书 和 成立于 2008/5/28.
标签:Load,core,Lazy,Pattern,System,using,public From: https://www.cnblogs.com/geovindu/p/17066173.html