Differences

This shows you the differences between two versions of the page.

--- vo_to_net:pcall [2018/07/11 08:35] – wolfgangriedmann
+++ vo_to_net:pcall [2018/07/29 05:22] (current) – wolfgangriedmann
@@ Line 4: / Line 4: @@
 The X# compiler needs a typed function pointer for ''PCall()'' to work (and you need the compiler switch /vo6 "Resolve function pointers to PTR"):
-<code>STATIC FUNCTION __GetRealOsVersion( struOS AS _winOSVERSIONINFOEX) AS DWORD PASCAL  // typed function pointer
+<code visualfoxpro>STATIC FUNCTION __GetRealOsVersion( struOS AS _winOSVERSIONINFOEX) AS DWORD PASCAL  // typed function pointer
   RETURN 0
 ....
@@ Line 10: / Line 10: @@
 dword( _cast , PCALL( hFunc ,@struOS) )</code>
 The alternative (to not define such a function) is to use ''PCallNative()'':
-<code>local hFunc as ptr
+<code visualfoxpro>local hFunc as ptr
 PCALLNative<dword>( hFunc ,@struOS )</code>
 The .NET way would be the definition of a delegate (i.e. a typed function pointer). Please see [[:delegates|Delegates]].
 A sample for the delegate version is the following:
-<code>delegate RtlGetVersionDelegate( struOS as _winOSVERSIONINFOEX) as dword
+<code visualfoxpro>delegate RtlGetVersionDelegate( struOS as _winOSVERSIONINFOEX) as dword
 local oFunc as RtlGetVersionDelegate
 oFunc := ( RtlGetVersionDelegate ) Marshal.GetDelegateForFunctionPointer( hFunc, TypeOf( RtlGetVersionDelegate ) )
 oFunc:Invoke( @struOS )</code>
+To simplify the code, a static method could help:
+<code visualfoxpro>static class DelegateHelper
+static method CreateDelegate<T>( hFunc as ptr ) as T
+  local oFunc as T
+  local oDelegate as object
+  oDelegate := Marshal.GetDelegateForFunctionPointer( hFunc, TypeOf( T ) )
+  oFunc := ( T ) oDelegate
+  return oFunc
+end class</code>
+and to be used:
+<code visualfoxpro>oFunc := DelegateHelper.CreateDelegate<RtlGetVersionDelegate>( hFunc )</code>
+(Code courtesy of Chris Pyrgas)
 The X# development team recommends the use of ''PCall()'' over ''PCallNative()'' because the X# compiler will build a delegate from the typed function pointer and use it.
@@ Line 28: / Line 46: @@
 For this reason I would recommend using PCall because the function name used in the declaration gives you full control of the parameter types in the delegate.''
-Please see major details in the X# Forum discussion:
+Please see more details in the X# Forum discussion:
 [[https://www.xsharp.info/forum/public-product/752-voxporter-icon-naming-problem#5355|www.xsharp.info/forum/public-product/752-voxporter-icon-naming-problem]]