服务定位器混乱

Question

我只是在编写一个实现ServiceLocator模式的类.

   public class ServiceFactory : IServiceFactory
    {
        private IDictionary<Type, object> instantiatedServices;

        public ServiceFactory()
        {
            instantiatedServices = new Dictionary<Type, object>();
        }

        public T GetService<T>() where T : class, new()
        {
            if (this.instantiatedServices.ContainsKey(typeof(T)))
            {
                return (T)this.instantiatedServices[typeof(T)];
            }
            else
            {
                T service = new T();

                instantiatedServices.Add(typeof(T), service);

                return service;
            }
        }
    }

现在我有几个问题:

1.)我应该从哪里打电话给这个班级？app.xaml.cs做wpf的东西？

2.)我应该注册服务,如果是,我应该在哪里注册？

3.)当我对服务"ICustomerService"进行延迟初始化时,为什么我应该为它创建一个Register(T服务)方法呢？这是双重工作.

4.)我应该去找服务定位器吗？

UPDATE

目前我觉得我必须为我个人目的强奸DI工具=>

App.xaml.cs =>这里我创建MainWindow并将其datacontext设置为MainViewModel.cs

public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            var mainVM = new MainViewModel();
            var mainWindow = new MainWindow();
            mainWindow.DataContext = mainVM;
            mainWindow.ShowDialog();            
        }        
    }

MainViewModel.cs =>这里我预装/设置我需要的某些Controller/ViewModel的数据,如LessonPlannerDailyViewModel或LessonPlannerWeeklyViewModel等...

public class MainViewModel : SuperViewModel
{     

        private LightCommand _newSchoolYearWizardCommand;       
        private LightCommand _showSchoolclassAdministrationCommand;
        private LightCommand _showLessonPlannerDailyCommand;
        private LightCommand _showLessonPlannerWeeklyCommand;  
        private LightCommand _openSchoolYearWizardCommand;

        private SuperViewModel _vm;
        private FadeTransition _fe = new FadeTransition();

        private readonly IMainRepository _mainService;
        private readonly ILessonPlannerService _lessonPlannerService;
        private readonly IAdminService _adminService;
        private readonly IDocumentService _documentService;     
        private readonly IMediator _mediator;

        private readonly  IDailyPlanner _dailyVM;
        private readonly  IWeeklyPlanner _weeklyVM;
        private SchoolclassAdministrationViewModel _saVM;    


        public MainViewModel()  
        {

            // These are a couple of services I create here because I need them in MainViewModel

            _mediator = new  Mediator();            
            _mainService = new MainRepository();
            _lessonPlannerService = new LessonPlannerService();
            _adminService = new AdminService();
            _documentService = new DocumentService();    

            this._mediator.Register(this);  

            InitSchoolclassAdministration();                     
        } 

        //... Create other ViewModel/Controller via button commands and their execute method
}  

在另一个ViewModel上是LessonPlannerDailyViewModel.cs =>这里我创建了一个可绑定的PeriodViewModel对象集合,它们为构造函数提供了一些服务.在下面的代码之后的下一段看到由ONE PeriodViewModel创建的DocumentListViewModel.cs,它再次获取服务 - 与我在MainViewModel中创建的相同... -

 public class LessonPlannerDailyViewModel : LessonPlannerBaseViewModel, IDailyPlanner
    {    
        private ILessonPlannerService _lpRepo;
        private IMainRepository _mainRepo;
        private IMediator _mediator;
        private IDocumentService _docRepo;

        private ObservableCollection<PeriodViewModel> _periodListViewModel;      

        private LightCommand _firstDateCommand;
        private LightCommand _lastDateCommand;
        private LightCommand _nextDateCommand;
        private LightCommand _previousDateCommand;  

        public LessonPlannerDailyViewModel(IMediator mediator, ILessonPlannerService lpRepo, IMainRepository mainRepo, IDocumentService docRepo)
        {
            _mediator = mediator;
            _lpRepo = lpRepo;
            _mainRepo = mainRepo;
            _docRepo = docRepo;

            _mediator.Register(this);

            SchoolYear schoolyear = _mainRepo.GetSchoolYear();

            MinDate = schoolyear.Start;
            MaxDate = schoolyear.End;         

            SelectedDate = DateTime.Now; 
        } 

        private void LoadLessonPlannerByDay(DateTime data)
        {
            _periodListViewModel = new ObservableCollection<PeriodViewModel>();

            _lpRepo.GetLessonPlannerByDay(data).ForEach(p =>
            {
                _periodListViewModel.Add(new PeriodViewModel(p, _lpRepo, _docRepo));
            });          

            PeriodListViewModel = _periodListViewModel;        
        } 

        private DateTime _selectedDate;
        public DateTime SelectedDate
        {
            get { return _selectedDate; }
            set
            {
                if (_selectedDate.Date == value.Date)
                    return;

                _selectedDate = value;
                this.RaisePropertyChanged("SelectedDate");

                LoadLessonPlannerByDay( value );
            }
        }

       // ...

}

PeriodViewModel.cs =>我的DataGrid中的每个DataRow都有一个Period和一个Period有一个dattablemplated到DocumentListViewModel的特定单元格 - Period 1有N Documents是关系FYI ...所以PeriodViewModel创建一个DocumentListViewModel.

public class PeriodViewModel : SuperViewModel
    {  
        private Period _period;
        private ILessonPlannerService _lpRepo;

        public PeriodViewModel(Period period, ILessonPlannerService lpRepo, IDocumentService docRepo)
        {            
            _period = period;
            _lpRepo = lpRepo;

            // Update properties to database
            this.PropertyChanged += (o, e) =>
            {
                switch (e.PropertyName)
                {
                    case "Homework": _lpRepo.UpdateHomeWork(PeriodNumber, LessonDayDate, Homework); break;
                    case "Content": _lpRepo.UpdateContent(PeriodNumber, LessonDayDate, Content); break;
                }
            };

            Documents = new DocumentListViewModel(_period.Id, period.Documents, docRepo); 
        }
   //...
}

DocumentListViewModel.cs =>这里我设置了添加/删除/打开文档的命令,这可以通过documentService/documentRepository来完成

public class DocumentListViewModel : SuperViewModel
    {
        private LightCommand _deleteDocumentCommand;
        private LightCommand _addDocumentCommand;
        private LightCommand _openDocumentCommand;      

        private int _parentId;

        private readonly IDocumentService _documentService;       

        public DocumentListViewModel(int parentId,ObservableCollection<Document> documents, IDocumentService documentService)
        {
            _parentId = parentId;
            _documentService = documentService;
            DocumentList = documents;
            SelectedDocuments = new ObservableCollection<Document>();
        } 

        // ...
} 

总结问题:你是否看到从顶部层叠服务的对象链:

MainViewodel - > LessonPlannerDailyViewModel - > PeriodViewModel - > DocumentListViewModel

我需要级联它们,因为如果我不使用静态服务定位器,我只能确保在级联服务时有一个服务实例...

这里DI工具如何帮助我具体做一个WPF应用程序MVVM模式下？

Answer 1

第四个问题是最容易回答的问题:不,你根本不应该选择Service Locator,因为它是一种反模式.

那么替代方案是什么？使用Register Resolve Release模式.这应该是回答其他问题的良好起点.