reflection - 我将如何发出歧视性工会？

Question

如果我有这样的事情：

type public ServiceActionType =
    | ServiceRequest
    | ServiceResponse
    | ServiceEventInvocation
    | ServiceEventSubscriptionRequest
    | ServiceMetadataRequest

然后如何将其中一项添加到堆栈中，如下所示：

IlGen.Emit(OpCodes.???, ???)

score 6 · Accepted Answer

现有答案很好，但请注意，Microsoft.FSharp.Reflection命名空间有一些帮助程序，可以轻松获取您关心的成员：

open Reflection
let cases = FSharpType.GetUnionCases(typeof<ServiceActionType>)
let serviceRequestMethod = FSharpValue.PreComputeUnionConstructorInfo(cases.[0])

结果是一样的，typeof<ServiceActionType>.GetMethod("get_ServiceRequest")但你不必担心知道编译的形式，这可能会根据联合案例是否有字段而有所不同。

score 4 · Accepted Answer

通常，可区分联合被编译为类层次结构（这意味着可区分联合的每个案例都有一个新的子类）。但是，在您的情况下，情况更简单，因为没有一个案例带有任何值。

如果您查看编译后的代码，您会看到生成的 .NET 表示形式为您提供如下内容：

class ServiceActionType {
  public static ServiceActionType ServiceRequest { get; }
  public static ServiceActionType ServiceResponse { get; }
  public static ServiceActionType ServiceEventInvocation { get; }
  // etc. for all the other cases
}

这意味着，如果您想构造可区分联合的值之一，您只需要发出对代表您想要的情况的（静态）属性的 getter 方法的调用。

如果您有一个带参数的案例，例如ServiceRequest of RequestInfo，那么生成的类将包含一个NewServiceRequest方法，该方法将采用必要的参数：

public static ServiceActionType NewServiceRequest(RequestInfo info);

也就是说，我不完全确定您为什么要这样做，因此发出代码可能不是最好的方法。您还可以考虑使用 F# 引用 - 它可以编译为动态方法 - 并且创建一个表示 DU 案例构造的引用非常容易使用Expr.NewUnionCase。

score 2 · Accepted Answer

让我们举个ServiceActionType.ServiceRequest例子。

我将以下内容放在 LINQPad（F# 程序模式）中以获取 IL（但您可以将ildasm.exe其用于相同目的）：

type public ServiceActionType =
    | ServiceRequest
    | ServiceResponse
    | ServiceEventInvocation
    | ServiceEventSubscriptionRequest
    | ServiceMetadataRequest

ServiceRequest.Dump()

它给了我：

IL_0001:  call        Query_qdoovg+ServiceActionType.get_ServiceRequest
IL_0006:  call        LINQPad.FSharpExtensions.Extensions.Dump

Dump:
IL_0000:  nop         
IL_0001:  ldarg.0     
IL_0002:  box         03 00 00 1B 
IL_0007:  call        LINQPad.FSharpExtensions.Extensions.Dump
IL_000C:  ret         

ServiceActionType.get_ServiceMetadataRequest:
IL_0000:  ldsfld      Query_qdoovg+ServiceActionType._unique_ServiceMetadataRequest
IL_0005:  ret         

ServiceActionType.get_IsServiceMetadataRequest:
IL_0000:  ldarg.0     
IL_0001:  call        Query_qdoovg+ServiceActionType.get_Tag
IL_0006:  ldc.i4.4    
IL_0007:  ceq         
IL_0009:  ret         

ServiceActionType.get_ServiceEventSubscriptionRequest:
IL_0000:  ldsfld      Query_qdoovg+ServiceActionType._unique_ServiceEventSubscriptionRequest
IL_0005:  ret         

ServiceActionType.get_IsServiceEventSubscriptionRequest:
IL_0000:  ldarg.0     
IL_0001:  call        Query_qdoovg+ServiceActionType.get_Tag
IL_0006:  ldc.i4.3    
IL_0007:  ceq         
IL_0009:  ret         

ServiceActionType.get_ServiceEventInvocation:
IL_0000:  ldsfld      Query_qdoovg+ServiceActionType._unique_ServiceEventInvocation
IL_0005:  ret         

ServiceActionType.get_IsServiceEventInvocation:
IL_0000:  ldarg.0     
IL_0001:  call        Query_qdoovg+ServiceActionType.get_Tag
IL_0006:  ldc.i4.2    
IL_0007:  ceq         
IL_0009:  ret         

ServiceActionType.get_ServiceResponse:
IL_0000:  ldsfld      Query_qdoovg+ServiceActionType._unique_ServiceResponse
IL_0005:  ret         

ServiceActionType.get_IsServiceResponse:
IL_0000:  ldarg.0     
IL_0001:  call        Query_qdoovg+ServiceActionType.get_Tag
IL_0006:  ldc.i4.1    
IL_0007:  ceq         
IL_0009:  ret         

ServiceActionType.get_ServiceRequest:
IL_0000:  ldsfld      Query_qdoovg+ServiceActionType._unique_ServiceRequest
IL_0005:  ret         

ServiceActionType.get_IsServiceRequest:
IL_0000:  ldarg.0     
IL_0001:  call        Query_qdoovg+ServiceActionType.get_Tag
IL_0006:  ldc.i4.0    
IL_0007:  ceq         
IL_0009:  ret         

ServiceActionType.get_Tag:
IL_0000:  ldarg.0     
IL_0001:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_0006:  ret         

ServiceActionType.__DebugDisplay:
IL_0000:  ldstr       "%+0.8A"
IL_0005:  newobj      Microsoft.FSharp.Core.PrintfFormat<Microsoft.FSharp.Core.FSharpFunc<Query_qdoovg+ServiceActionType,System.String>,Microsoft.FSharp.Core.Unit,System.String,System.String,System.String>..ctor
IL_000A:  call        Microsoft.FSharp.Core.ExtraTopLevelOperators.PrintFormatToString
IL_000F:  ldarg.0     
IL_0010:  callvirt    Microsoft.FSharp.Core.FSharpFunc<Query_qdoovg+ServiceActionType,System.String>.Invoke
IL_0015:  ret         

ServiceActionType.CompareTo:
IL_0000:  nop         
IL_0001:  ldarg.0     
IL_0002:  ldnull      
IL_0003:  cgt.un      
IL_0005:  brfalse.s   IL_0027
IL_0007:  ldarg.1     
IL_0008:  ldnull      
IL_0009:  cgt.un      
IL_000B:  brfalse.s   IL_0025
IL_000D:  ldarg.0     
IL_000E:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_0013:  stloc.0     
IL_0014:  ldarg.1     
IL_0015:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_001A:  stloc.1     
IL_001B:  ldloc.0     
IL_001C:  ldloc.1     
IL_001D:  bne.un.s    IL_0021
IL_001F:  ldc.i4.0    
IL_0020:  ret         
IL_0021:  ldloc.0     
IL_0022:  ldloc.1     
IL_0023:  sub         
IL_0024:  ret         
IL_0025:  ldc.i4.1    
IL_0026:  ret         
IL_0027:  ldarg.1     
IL_0028:  ldnull      
IL_0029:  cgt.un      
IL_002B:  brfalse.s   IL_002F
IL_002D:  ldc.i4.m1   
IL_002E:  ret         
IL_002F:  ldc.i4.0    
IL_0030:  ret         

ServiceActionType.CompareTo:
IL_0000:  nop         
IL_0001:  ldarg.0     
IL_0002:  ldarg.1     
IL_0003:  unbox.any   Query_qdoovg.ServiceActionType
IL_0008:  call        Query_qdoovg+ServiceActionType.CompareTo
IL_000D:  ret         

ServiceActionType.CompareTo:
IL_0000:  nop         
IL_0001:  ldarg.1     
IL_0002:  unbox.any   Query_qdoovg.ServiceActionType
IL_0007:  stloc.0     
IL_0008:  ldarg.0     
IL_0009:  ldnull      
IL_000A:  cgt.un      
IL_000C:  brfalse.s   IL_0033
IL_000E:  ldarg.1     
IL_000F:  unbox.any   Query_qdoovg.ServiceActionType
IL_0014:  ldnull      
IL_0015:  cgt.un      
IL_0017:  brfalse.s   IL_0031
IL_0019:  ldarg.0     
IL_001A:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_001F:  stloc.1     
IL_0020:  ldloc.0     
IL_0021:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_0026:  stloc.2     
IL_0027:  ldloc.1     
IL_0028:  ldloc.2     
IL_0029:  bne.un.s    IL_002D
IL_002B:  ldc.i4.0    
IL_002C:  ret         
IL_002D:  ldloc.1     
IL_002E:  ldloc.2     
IL_002F:  sub         
IL_0030:  ret         
IL_0031:  ldc.i4.1    
IL_0032:  ret         
IL_0033:  ldarg.1     
IL_0034:  unbox.any   Query_qdoovg.ServiceActionType
IL_0039:  ldnull      
IL_003A:  cgt.un      
IL_003C:  brfalse.s   IL_0040
IL_003E:  ldc.i4.m1   
IL_003F:  ret         
IL_0040:  ldc.i4.0    
IL_0041:  ret         

ServiceActionType.GetHashCode:
IL_0000:  nop         
IL_0001:  ldarg.0     
IL_0002:  ldnull      
IL_0003:  cgt.un      
IL_0005:  brfalse.s   IL_003C
IL_0007:  ldc.i4.0    
IL_0008:  stloc.0     
IL_0009:  ldarg.0     
IL_000A:  call        Query_qdoovg+ServiceActionType.get_Tag
IL_000F:  switch      (IL_0028, IL_002C, IL_0030, IL_0034, IL_0038)
IL_0028:  ldc.i4.0    
IL_0029:  stloc.0     
IL_002A:  ldloc.0     
IL_002B:  ret         
IL_002C:  ldc.i4.1    
IL_002D:  stloc.0     
IL_002E:  ldloc.0     
IL_002F:  ret         
IL_0030:  ldc.i4.2    
IL_0031:  stloc.0     
IL_0032:  ldloc.0     
IL_0033:  ret         
IL_0034:  ldc.i4.3    
IL_0035:  stloc.0     
IL_0036:  ldloc.0     
IL_0037:  ret         
IL_0038:  ldc.i4.4    
IL_0039:  stloc.0     
IL_003A:  ldloc.0     
IL_003B:  ret         
IL_003C:  ldc.i4.0    
IL_003D:  ret         

ServiceActionType.GetHashCode:
IL_0000:  nop         
IL_0001:  ldarg.0     
IL_0002:  call        Microsoft.FSharp.Core.LanguagePrimitives.get_GenericEqualityComparer
IL_0007:  call        Query_qdoovg+ServiceActionType.GetHashCode
IL_000C:  ret         

ServiceActionType.Equals:
IL_0000:  nop         
IL_0001:  ldarg.0     
IL_0002:  ldnull      
IL_0003:  cgt.un      
IL_0005:  brfalse.s   IL_0026
IL_0007:  ldarg.1     
IL_0008:  isinst      Query_qdoovg.ServiceActionType
IL_000D:  stloc.0     
IL_000E:  ldloc.0     
IL_000F:  brfalse.s   IL_0024
IL_0011:  ldarg.0     
IL_0012:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_0017:  stloc.1     
IL_0018:  ldloc.0     
IL_0019:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_001E:  stloc.2     
IL_001F:  ldloc.1     
IL_0020:  ldloc.2     
IL_0021:  ceq         
IL_0023:  ret         
IL_0024:  ldc.i4.0    
IL_0025:  ret         
IL_0026:  ldarg.1     
IL_0027:  ldnull      
IL_0028:  cgt.un      
IL_002A:  ldc.i4.0    
IL_002B:  ceq         
IL_002D:  ret         

ServiceActionType.Equals:
IL_0000:  nop         
IL_0001:  ldarg.0     
IL_0002:  ldnull      
IL_0003:  cgt.un      
IL_0005:  brfalse.s   IL_0022
IL_0007:  ldarg.1     
IL_0008:  ldnull      
IL_0009:  cgt.un      
IL_000B:  brfalse.s   IL_0020
IL_000D:  ldarg.0     
IL_000E:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_0013:  stloc.0     
IL_0014:  ldarg.1     
IL_0015:  ldfld       Query_qdoovg+ServiceActionType._tag
IL_001A:  stloc.1     
IL_001B:  ldloc.0     
IL_001C:  ldloc.1     
IL_001D:  ceq         
IL_001F:  ret         
IL_0020:  ldc.i4.0    
IL_0021:  ret         
IL_0022:  ldarg.1     
IL_0023:  ldnull      
IL_0024:  cgt.un      
IL_0026:  ldc.i4.0    
IL_0027:  ceq         
IL_0029:  ret         

ServiceActionType.Equals:
IL_0000:  nop         
IL_0001:  ldarg.1     
IL_0002:  isinst      Query_qdoovg.ServiceActionType
IL_0007:  stloc.0     
IL_0008:  ldloc.0     
IL_0009:  brfalse.s   IL_0013
IL_000B:  ldarg.0     
IL_000C:  ldloc.0     
IL_000D:  call        Query_qdoovg+ServiceActionType.Equals
IL_0012:  ret         
IL_0013:  ldc.i4.0    
IL_0014:  ret         

ServiceActionType..ctor:
IL_0000:  ldarg.0     
IL_0001:  call        System.Object..ctor
IL_0006:  ldarg.0     
IL_0007:  ldarg.1     
IL_0008:  stfld       Query_qdoovg+ServiceActionType._tag
IL_000D:  ret

执行指令以获取堆栈上的值IL_0001: call Query_qdoovg+ServiceActionType.get_ServiceRequest的位在哪里。callServiceActionType.ServiceRequest

可以像这样发出：il.Emit(OpCodes.Call, typeof<ServiceActionType>.GetMethod("get_ServiceRequest"))

reflection - 我将如何发出歧视性工会？

3 回答 3

Related

Reference