不久前我在codereview.stackexchange.com上发布了this review ...我觉得它可能更适合stackoverflow,因为它更像是一个问题,而不是代码审查。
这需要一点解释,请容忍我,,,__。
我正在开发一个电子商务网站在ASP.NET的MVC。用户可以在网站上发布不同类型的广告。
我正在使用继承来定义我的广告类型,这个问题是关于利用层次结构来删除控制器和视图中的重复代码。
我有不同的广告类型:SimpleAd
,Car
和RealEstateRental
。
每一个广告都是从AdBase派生出来的,它具有所有的共同属性:
public abstract class AdBase
{
public long AdBaseId { get; set; }
public bool IsActive { get; set; }
public long UserId { get; set; }
public string Title { get; set; }
public short AdDurationInDays { get; set; }
public string PhotosFolder { get; set; }
}
现在其他的广告都是从这个基类派生的:
public class SimpleAd : AdBase
{
public decimal Price { get; set; }
}
public class Car : AdBase
{
public decimal Price { get; set; }
public string Make { get; set; }
}
public class RealEstateRental : AdBase
{
public decimal WeeklyRent { get; set; }
public DateTime AvailableFrom { get; set; }
public short NoOfBedrooms { get; set; }
public short NoOfBathrooms { get; set; }
}
我使用Entity Framework与数据库交互,并使用Unit of Work和Repository模式:
我有一个包含所有常见广告方法的通用AdBaseRepository:
public abstract class AdBaseRepository<TEntity> where TEntity : AdBase
{
protected readonly ApplicationDbContext Context;
public AdBaseRepository(ApplicationDbContext context)
{
Context = context;
}
public TEntity Get(long adBaseId)
{
return Context.AdBase.OfType<TEntity>()
.Where(r => r.IsActive == true && r.AdBaseId == adBaseId)
.FirstOrDefault();
}
// more common methods here...
}
其他广告存储库继承自上面的类:
public class SimpleAdRepository : AdBaseRepository<SimpleAd>
{
public SimpleAdRepository(ApplicationDbContext context) : base(context)
{
}
}
public class CarRepository : AdBaseRepository<Car>
{
public CarRepository(ApplicationDbContext context) : base(context)
{
}
// methods which apply only to car here...
}
这是我的工作单位:
public class UnitOfWork
{
protected readonly ApplicationDbContext Context;
public UnitOfWork(ApplicationDbContext context)
{
Context = context;
SimpleAd = new SimpleAdRepository(Context);
RealEstateRental = new RealEstateRentalRepository(Context);
Car = new CarRepository(Context);
}
public SimpleAdRepository SimpleAd { get; private set; }
public RealEstateRentalRepository RealEstateRental { get; private set; }
public CarRepository Car { get; private set; }
public int SaveChanges()
{
return Context.SaveChanges();
}
public void Dispose()
{
Context.Dispose();
}
}
到目前为止我对一切都很满意...但问题是我不知道如何在我的控制器和视图中利用这种继承层次结构。
目前,我有3个控制器:SimpleAdController
、CarController
和RealEstateRentalController
public class SimpleAdController : ControllerBase
{
private UnitOfWork _unitOfWork;
public SimpleAdController(UnitOfWork unitOfWork)
{
_unitOfWork = unitOfWork;
}
[HttpGet]
// display specific ad
public ActionResult Display(long id)
{
SimpleAd simpleAd = _unitOfWork.SimpleAd.Get(id);
/*
* I have not included my ViewModel Classes in this question to keep
* it small, but the ViewModels follow the same inheritance pattern
*/
var simpleAdDetailsViewModel = Mapper.Map<SimpleAdDetailsViewModel>(simpleAd);
return View(simpleAdDetailsViewModel);
}
}
CarController
和RealEstateRentalController
有相同的Display
方法,除了广告的类型不同(例如在CarController
中我有):
public ActionResult Display(long id)
{
Car car = _unitOfWork.Car.Get(id);
var carViewModel = Mapper.Map<CarViewModel>(car);
return View(car);
}
我想要实现的是创建一个AdBaseController
,将所有常用方法放入其中,如下所示:
public class AdBaseController : ControllerBase
{
private UnitOfWork _unitOfWork;
public AdBaseController(UnitOfWork unitOfWork)
{
_unitOfWork = unitOfWork;
}
// Display for generic ad type
[HttpGet]
public ActionResult Display(long id)
{
// SimpleAd simpleAd = _unitOfWork.SimpleAd.Get(id);
/*
* I need to replace the above line with a generic ad type...
* something like: _unitOfWork<TAd>.GenericAdRepository.Get(id)
*/
// var simpleAdDetailsViewModel = Mapper.Map<SimpleAdDetailsViewModel>(simpleAd);
// return View(simpleAdDetailsViewModel);
/*
* similarly I have to replace the above 2 lines with a generic type
*/
}
}
如果我这样做,那么我的广告控制器可以继承它,我不需要在每个广告控制器中重复相同的显示方法……但是我需要让我的UnitOfWork
泛型...或者有2个UoW (通用和非通用)...我不确定这是不是一个好主意?关于拥有 AdBaseController
的任何建议
类似地,我在视图中重复了很多代码。例如,这是显示SimpleAdView
<div class="row">
<div class="col-l">
@*this partial view shows Ad photos and is common code for all ad types*@
@Html.Partial("DisplayAd/_Photos", Model)
</div>
<div class="col-r">
<div class="form-row">
@*Common in all ads*@
<h5>@Model.Title</h5>
</div>
@*showing ad specific fields here*@
<div class="form-row">
<h5 class="price">$@Model.Price</h5>
</div>
@*Ad heading is common among all ad types*@
@Html.Partial("DisplayAd/_AdBaseHeading", Model)
</div>
</div>
@*Ad Description is common among all ad types*@
@Html.Partial("DisplayAd/_Description", Model)
这是我的display CarView
<div class="row">
<div class="col-l">
@*Common in all ads*@
@Html.Partial("DisplayAd/_Photos", Model)
</div>
<div class="col-r">
<div class="form-row">
@*Common in all ads*@
<h5>@Model.Title</h5>
</div>
@*Price and Make are specific to Car*@
<div class="form-row">
<h5 class="price">$@Model.Price</h5>
</div>
<div class="form-row">
<h5 class="make">@Model.Make</h5>
</div>
@*Common in all ads*@
@Html.Partial("DisplayAd/_AdBaseHeading", Model)
</div>
</div>
@*Common in all ads*@
@Html.Partial("DisplayAd/_Description", Model)
再一次,我感觉我在每个视图中重复了很多代码。我试图通过将它们放在公共的局部视图中来减少重复代码的数量。我不确定是否有更好的方法来做这件事?
发布于 2018-09-18 22:23:06
从技术上讲,这是可能的。对于类似的实体,您可以引入枚举,并使用它来指示您在controller
中处理的实体类型。您可以创建通用视图来处理类似的广告(当然,您需要根据模型广告类型显示/隐藏相应的UI元素)。这是controller
的伪代码,用来说明这个想法:
using System.Threading.Tasks;
using AutoMapper;
using MyNamespace.Data;
using Microsoft.AspNetCore.Mvc;
using MyNamespace.ViewModels;
namespace MyNamespace
{
public enum AdType
{
[Description("Simple Ad")]
SimpleAd = 0,
[Description("Car")]
Car = 1,
[Description("Real Estate Rental")]
RealEstateRental = 2
}
public class AdController : Controller
{
private readonly ApplicationDbContext _context;
private readonly IMapper _mapper;
public AdController(
ApplicationDbContext context,
IMapper mapper)
{
_context = context;
_mapper = mapper;
}
[HttpGet("Ad/{type}")]
public IActionResult Index(AdType? type = AdType.SimpleAd)
{
switch (type)
{
case AdType.RealEstateRental:
return RedirectToAction("RealEstateRental");
case AdType.Car:
return RedirectToAction("Car");
case AdType.SimpleAd:
default:
return RedirectToAction("SimpleAd");
}
}
[HttpGet("Ad/Car")]
public IActionResult Car()
{
return View("Index", AdType.Car);
}
[HttpGet("Ad/RealEstateRental")]
public IActionResult RealEstateRental()
{
return View("Index", AdType.RealEstateRental);
}
[HttpGet("Ad/SimpleAd")]
public IActionResult SimpleAd()
{
return View("Index", AdType.SimpleAd);
}
[HttpGet("Ad/List/{type}")]
public async Task<IActionResult> List(AdType type)
{
// var list = ... switch to retrieve list of ads via switch and generic data access methods
return list;
}
[HttpGet("Ad/{type}/Details/{id}")]
public async Task<IActionResult> Details(AdType type, int id)
{
var ad = // ... switch by type to retrieve list of ads via switch and generic data access methods
if (ad == null) return NotFound($"Ad not found.");
// for instance - configure mappings via Automapper from DB entity to model views
var model = _mapper.Map<AdViewModel>(ad);
// Note: view will have to detect the exact ad instance type and show/hide corresponding UI fields
return View(model);
}
[HttpGet("Ad/{type}/Add/")]
public IActionResult Add(AdType type)
{
var ad = // ... switch by type to validate/add new entity
return View(_mapper.Map<AdEditModel>(ad));
}
[HttpPost("Ad/{type}/Add/")]
public async Task<IActionResult> Add(AdEditModel model)
{
// detect ad type and save
return View(model);
}
[HttpGet("Ad/{type}/Edit/{id}")]
public async Task<IActionResult> Edit(AdType type, int id)
{
// similar to Add
return View(model);
}
[HttpPost("Ad/{type}/Edit/{id}")]
public async Task<IActionResult> Edit(AdEditModel model)
{
// similar to Add
return View(model);
}
// And so on
}
}
但我应该指出,UI相关代码中的继承最终会带来更多的问题而不是好处。维护和保持代码的整洁变得更加复杂。因此,将所有Views
和Controllers
分开更有意义,即使它们的代码彼此非常接近。您可以在DI服务(也称为business logic
)或类似层下开始优化“重复代码”的使用。
UI级别的repeated code
问题应该通过提取组件(也就是controls
、partial views
、view components
)来解决。控制器继承是可能的,但会使代码更难维护。
发布于 2018-09-19 20:19:58
更多的抽象->更多的抽象泄漏。
我有完整的解决方案,如何使用exression树从EF模型定义生成控制器
检查一下,删除所有“重复代码”后,控制器的代码看起来是什么样子:
或者这个(“角色”可以在从AD导入"Users“时创建)
start上的这些模块配置了具有许多功能的完整控制器(例如,行版本支持,sql server约束错误解析器等,一对多,多对多,未处理的异常支持)
static ControllerMeta<User, int> meta = new ControllerMeta<User, int>(
// how to find entity by "id"
findByIdExpression: id => e => e.UserId == id,
// how to extract "id" from http responce
keyConverter: Converters.TryParseInt,
// configure EF includes for Index page
indexIncludes: chain => chain
.IncludeAll(e => e.UserPrivilegeMap)
// ... and so on, try to read it
但这些定义实际上是一种新的内部DSL。实际上,你在问“如何编写新的DSL,用更大的模块定义控制器/页面”。答案是-这很容易,但人们坚持使用通用语言是有原因的。这是因为它是“一般”的。
附注:一个细节:如果你想要“完整的控制器”可以在运行时收缩/配置,因此你被迫自己解析http请求-并忽略MS参数绑定模型-这是因为BindAttribute
-重要的绑定修饰符-不能在运行时以简单的方式“设置”。对于许多人来说-即使他们在参数列表中丢失了"int id“-代价也太高了。即使拒绝MS参数绑定是非常合乎逻辑的:当你要神奇地配置整个控制器时,为什么你需要保持MS参数绑定的魔力呢?
发布于 2018-09-12 06:42:57
如果我误解了,请原谅,但如果您添加了一个通用的UOW,在我看来,您可以这样做:我不明白为什么这样做是不好的
public class AdBaseController : ControllerBase
{
private IUnitOfWork _unitOfWork;
public AdBaseController(IUnitOfWork unitOfWork)
{
_unitOfWork = unitOfWork;
}
public ActionResult GetDisplayAction<TAd, TViewModel>(long id)
{
SimpleAd simpleAd = _unitOfWork<TAd>.GenericAdRepository.Get(id)
var viewModel = Mapper.Map<TViewModel>(simpleAd);
return View(viewModel);
}
}
public class SimpleAdController : ControllerBase
{
public SimpleAdController(IUnitOfWork unitOfWork) : base(unitOfWork)
{
}
[HttpGet]
public ActionResult Display(long id)
{
return GetDisplayAction<AdType, ViewModelType>();
}
}
https://stackoverflow.com/questions/52284912
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