如何调用Web API Controller的构造函数？

Question

根据这篇文章,一个Controller应该有一个构造函数来获取要传入的接口,一个la:

public class DuckbillsController : ApiController
{
    IDuckbillRepository _platypiRepository;

    public DuckbillsController(IDuckbillRepository platypiRepository)
    {
        if (platypiRepository == null)
        {
            throw new ArgumentNullException("platypiRepository is null");
        }
        _platypiRepository = platypiRepository;
    }
}

但这个构造函数是如何调用的呢？通过客户端调用此类中包含的Web API方法,但是如何通过接口类型传递？或者这不一定发生(构造函数没有被任何人/从任何地方明确调用)？

UPDATE

规范示例在接口声明之前显示"private readonly",但是编译它不是必需的.是否有编译,我的意思是引人注目,有理由,让我先加上"私人只读"？

Answer 1

由于此处没有相关文档(官方文档仅讨论使用Unity进行此操作).这是你如何做到的.

该HttpConfiguration.DependencyResolver属性的实例IDependecyResolver基本上是一个服务定位器(您要求一个类型的实例,它知道如何创建它).我想要的是提供我自己的控制器实例.

使用如下:

config.DependencyResolver = 
   new OverriddenWebApiDependencyResolver(config.DependencyResolver)
   .Add(typeof(ScoreboardController), () => 
                                    new ScoreboardController(Messages) 
   ); 

像这样实现:

/// <summary>
/// The standard web api dependency resolver cannot inject dependencies into a controller 
/// use this as a simple makeshift IoC
/// </summary>
public class OverriddenWebApiDependencyResolver : WebApiOverrideDependency<IDependencyResolver >, IDependencyResolver {
    public OverriddenWebApiDependencyResolver Add(Type serviceType, Func<object> initializer) {
        provided.Add(serviceType, initializer);
        return this;
    }
    public IDependencyScope BeginScope() => new Scope(inner.BeginScope(), provided);
    public OverriddenWebApiDependencyResolver(IDependencyResolver inner) : base(inner, new Dictionary<Type, Func<object>>()) { }
    public class Scope : WebApiOverrideDependency<IDependencyScope>, IDependencyScope {
        public Scope(IDependencyScope inner, IDictionary<Type, Func<object>> provided) : base(inner, provided) { }
    }
}
public abstract class WebApiOverrideDependency<T> : IDependencyScope where T : IDependencyScope {
    public void Dispose() => inner.Dispose();
    public Object GetService(Type serviceType) {
        Func<Object> res;
        return provided.TryGetValue(serviceType, out res) ? res() : inner.GetService(serviceType);
    }

    public IEnumerable<Object> GetServices(Type serviceType) {
        Func<Object> res;
        return inner.GetServices(serviceType).Concat(provided.TryGetValue(serviceType, out res) ? new[] { res()} : Enumerable.Empty<object>());
    }
    protected readonly T inner;
    protected readonly IDictionary<Type, Func<object>> provided;
    public WebApiOverrideDependency(T inner, IDictionary<Type, Func<object>> provided) {
        this.inner = inner;
        this.provided = provided;
    }

}

诀窍是你实际上必须实现IDependencyScope 两次 - 一次为IDependencyResolver一次,一次为每个请求创建的范围.

Answer 2

控制器工厂为您创建它们......您需要查看依赖注入.

尝试Autofac,它与MVC有很好的集成.

Answer 3

你必须使用依赖注入(structuremap,ninject).如果你不想使用DI,那么你必须提供一个重载构造函数,如下所示

public DuckbillsController():this( new DuckbillRepository())
{
}