如何反映接口类型< t>在运行时 [英] How to reflect an interfaced type<t> at runtime

问题描述

我有多个数据点和每个数据点的关联数据处理器。

I have multiple data-points and an associated data-processor for each.

public interface IDataPointProcessor<T> where T : DataPointInputBase
{
    DataPointOutputBase GetOutput(T input);
}

我从文件中加载了数据点列表，并希望使用

I load a list of data points from a file and wish to process them using its single associated processor.

foreach (DataPointInputBase item in input.DataPoints)
{
    //assuming item coming in is of type 'X' how do I get correct processor
    var type = typeof(IDataPointProcessor<X>);
    var types = AppDomain.CurrentDomain.GetAssemblies()
                .SelectMany(s => s.GetTypes())
                .Where(p => type.IsAssignableFrom(p) && !p.IsAbstract);

    IDataPointProcessor<X> matchedType = ??

}

如何求解 X，以便实例化

How do I solve for 'X' so I can instantiate it and process the input?

更新＃1
从下面结合Slava和Lucky的答案，我得到了以下内容，但是它引发异常-对象与目标类型不匹配。即使在调试器中一切似乎都可以匹配。是否可以强制转换为IDataPointProcessor<>并干净地调用接口方法，即：instance.GetOutput（item）;

Update #1 Combining answers from below from Slava and Lucky I get the following, but it throws an exception - 'Object does not match target type.' even though it all seems to match up ok in debugger. Is it possible to cast as IDataPointProcessor<> and call interface method cleanly, ie: instance.GetOutput(item);

foreach (DataPointInputBase item in input.DataPoints)
{
    Type typeGenArg = item.GetType();

    Type typeInterfaceGen = typeof(IDataPointProcessor<>).MakeGenericType(typeGenArg);

    Type type = AppDomain.CurrentDomain.GetAssemblies()
        .SelectMany(x => x.GetTypes())
        .Where(x => typeInterfaceGen.IsAssignableFrom(x) && !x.IsAbstract)
        .FirstOrDefault();

    Type genericType = typeof(IDataPointProcessor<>);

    Type dependedGenericType = genericType.MakeGenericType(typeof(DataPointInputBase));

    var method = dependedGenericType.GetMethod("GetOutput");
    var instance = Activator.CreateInstance(type);
    //currently throws:System.Reflection.TargetException: 'Object does not match target type.'
    var result = method.Invoke(instance, new object[] { item });
    //Ideally I want to do this and avoid the magic strings etc
    //var temp_output = instance.GetOutput(item);
}

更新＃2
事情在移动我已经对 Age_Input类型进行了硬编码，以验证事情是否正常。我缺少什么来动态调用硬编码位？

Update #2 To keep things moving I've hard coded the type 'Age_Input' to validate the thing works. What am I missing to call the hard coded bit dynamically?

我应该能够将实例转换为 IDataPointProcessor< IDataPointInput> 并在接口上调用 GetOutput（）

I should be able to cast instance to IDataPointProcessor<IDataPointInput> and call GetOutput() on the interface

foreach (IDataPointInput item in input.DataPoints)
{
    Type typeGenArg = item.GetType();

    Type typeInterfaceGen = typeof(IDataPointProcessor<>).MakeGenericType(typeGenArg);

    Type type = AppDomain.CurrentDomain.GetAssemblies()
        .SelectMany(x => x.GetTypes())
        .Where(x => typeInterfaceGen.IsAssignableFrom(x) && !x.IsAbstract)
        .FirstOrDefault();

    Type genericType = typeof(IDataPointProcessor<>);

    Type dependedGenericType = genericType.MakeGenericType(typeof(IDataPointInput));

    var instance = Activator.CreateInstance(type);

    if (instance is IDataPointProcessor<Age_Input>)//hard-coded
    {
        var processor = instance as IDataPointProcessor<Age_Input>;
        Age_Input temp = item as Age_Input;
        var result = processor.GetOutput(temp);
    }
    if (instance is DataPointProcessorBase<DataPointInputBase>)
    {
        //false
    }
    if (instance is IDataPointProcessor<DataPointInputBase>)
    {
        //false
    }
    if (instance is IDataPointProcessor<IDataPointInput>)
    {
        //false - shouldn't this work?
    }
}

Age_Input是一个琐碎的类，继承自一个笨拙的基类类和空接口

Age_Input is a trivial class, inheriting from a dumb base class and an empty interface

public class Age_Input : DataPointInputBase, IDataPointInput
{
    public int AgeExact { get; set; }
} 

public class DataPointInputBase : IDataPointInput
{
}
public interface IDataPointInput
{
}

处理器类同样简单

 public abstract class DataPointProcessorBase<T> : IDataPointProcessor<T> where T : IDataPointInput, new()
    {
        //public abstract DataPointOutputBase GetOutput(DataPointInputBase input);
        public abstract DataPointOutputBase GetOutput(T input);
    }

    public interface IDataPointInput
    {
    }

    public interface IDataPointProcessor<IDataPointInput> 
    {
        DataPointOutputBase GetOutput(IDataPointInput input);
    }

推荐答案

通常如此，如果可以避免反射，通常情况会更好。我用一点点的代码味道换了一个更简单的解决方案。

So as is usually the case, if you can avoid Reflection you're generally better off. I traded a tiny bit of code smell for a much simpler solution.

本质上，我回到了基础知识并使用了哑巴接口，并在输入中返回了一个辅助方法

Essentially I went back to basics and used dumb interfaces, and a helper method on the input that returned a primed instance of the corresponding processor.

现在，我的大反射循环被替换为：

Now my big reflection loop is replaced with this:

foreach (IDataPointInput item in input)
{
    IDataPointProcessor processor = item.GetProcessor();
    IDataPointOutput output = processor.GetOutput();
}

代码气味是这个-不是问题

The code smell is this - not an issue

public override IDataPointProcessor GetProcessor()
{
    return new Age_Processor(this);
}

下面的完整代码

#region Interfaces
public interface IDataPointProcessor
{
    IDataPointOutput GetOutput();
}

public interface IDataPointInput
{
    IDataPointProcessor GetProcessor();
}

public interface IDataPointOutput
{
    List<string> DebugStrings { get; set; }
} 
#endregion

#region Base Classes
public abstract class DataPointProcessorBase : IDataPointProcessor
{
    public abstract IDataPointOutput GetOutput();
}

public abstract class DataPointInputBase : IDataPointInput
{
    public abstract IDataPointProcessor GetProcessor();
}

public abstract class DataPointOutputBase : IDataPointOutput
{
    public List<string> DebugStrings { get; set; }

    public DataPointOutputBase()
    {
        DebugStrings = new List<string>();
    }
} 
#endregion

public class Age_Output : DataPointOutputBase
{
}

public class Age_Input : DataPointInputBase
{
    public int AgeExact { get; set; }

    public override IDataPointProcessor GetProcessor()
    {
        return new Age_Processor(this);
    }
}

public class Age_Processor : DataPointProcessorBase
{
    public Age_Input Input { get; set; }
    public Age_Processor(Age_Input input)
    {
        Input = input;
    }

    public override IDataPointOutput GetOutput()
    {
        Age_Output output = new Age_Output();


        if (Input.AgeExact > 30)
        {
            output.DebugStrings.Add("Getting old");
        }
        else
        {
            output.DebugStrings.Add("Still young");
        }
        return output;
    }
}

public class DecisionEngine
{
    public void GetDecisions()
    {
        List<IDataPointInput> input = new List<IDataPointInput>();
        input.Add(new Age_Input { AgeExact = 44 });
        foreach (IDataPointInput item in input)
        {
            IDataPointProcessor processor = item.GetProcessor();
            IDataPointOutput output = processor.GetOutput();

        }
    }
}

这篇关于如何反映接口类型&lt; t&gt;在运行时的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！