Unity 2.0:如何使用ResolverOverride解决？

Question

我开始用Unity做越来越多的工作.我注意到解析方法需要一个PARAMS参数ResolverOverride.

有人可以给我一个例子,我可以如何使用ResolverOverride或指向我一些其他来源,我可以得到更多的线索.

Answer 1

您已经注意到这是Unity 2的一个新的(非常酷的功能).这个功能让你

• 在解析类时将参数传递给构造函数.在unity 1中,当您通过新的InjectionConstructor(...)注册类型时,您只能设置一个值

有 ParameterOverride : ResolverOverride

一个ResolverOverride类,它允许您覆盖传递给构造函数的命名参数.

• 与依赖关系相同 DependencyOverride : ResolverOverride

一个类,只要存在给定类型的依赖关系,就会覆盖注入的值,而不管它在对象图中出现的位置.

• 与属性相同 PropertyOverride : ResolverOverride

ResolverOverride,允许您覆盖指定属性的值.

例

using System;
using Microsoft.Practices.Unity;

namespace ConsoleApplication1 {
    class Program {
        static void Main(string[] args) {

            var container = new UnityContainer();

            //ParameterOverride example

            container.RegisterType<IConcreteService, ConcreteService>(
                new InjectionConstructor(7) //Old way to pass value to constructor - not flexible. 
                                            //All resolved (without override which appears only in unity 2.0) classes will have val=7
                );

            var service0 = container.Resolve<IConcreteService>();
            Console.WriteLine(service0.Val); //prints 7

            var service = container.Resolve<IConcreteService>(new ParameterOverride("val", 3));
            Console.WriteLine(service.Val); // prints 3

            var service2 = container.Resolve<IConcreteService>(new ParameterOverride("val", 5));
            Console.WriteLine(service2.Val); // prints 5

            Console.ReadLine();

            //DependencyOverride example

            var b0 = container.Resolve<B>(new DependencyOverride<IConcreteService>(new ConcreteService(42)));
            Console.WriteLine(b0.Service.Val); //print 42
            Console.WriteLine(b0.Service1.Val); //print 42

            var b = container.Resolve<B>(new DependencyOverride<IConcreteService>(new ConcreteService(-42)));
            Console.WriteLine(b.Service.Val); // print -42
            Console.WriteLine(b.Service1.Val); // print -42

            Console.ReadLine();

            //PropertyOverride example 

            var b1 = container.Resolve<B>(new PropertyOverride("Service", new ConcreteService(42)), 
                new PropertyOverride("Service1", new ConcreteService(-42)));
            Console.WriteLine(b1.Service.Val); //print 42
            Console.WriteLine(b1.Service1.Val); //print -42

            Console.ReadLine();



        }
    }

    public interface IConcreteService {
        int Val { get; set; }
    }
    public class ConcreteService : IConcreteService {

        public int Val { get; set; }

        public ConcreteService(int val) {
            Val = val;
        }
    }

    public class B {
        [Dependency]
        public IConcreteService Service{ get; set; }

        [Dependency]
        public IConcreteService Service1 { get; set; }

    }
}

不知道为什么谷歌对此保持沉默.

报价来自Unity源代码xml docs.

Answer 2

为了防止有人感兴趣,我已经制作了一个扩展方法,使得解析的语法ParameterOverride更易于阅读.方法如下:

public static class UnityExtensions
{
    public static T Resolve<T>(this IUnityContainer container, object parameterOverrides)
    {
        var properties = parameterOverrides
            .GetType()
            .GetProperties(BindingFlags.Public | BindingFlags.Instance);
        var overridesArray = properties
            .Select(p => new ParameterOverride(p.Name, p.GetValue(parameterOverrides, null)))
            .Cast<ResolverOverride>()
            .ToArray();
        return container.Resolve<T>(null, overridesArray); //null needed to avoid a StackOverflow :)
    }
}

有了这个,您可以重写ParameterOverride示例,如下所示:

var service = container.Resolve<IConcreteService>(new {val=3});

我希望这对某些人有用......

Answer 3

只是为了添加我的2c.你可以像这样添加一个ParameterOverrides:

Container.Resolve<IConcreteService>(new ParameterOverrides
{                                                                                   
  {"val", 42}
});