Sharing function that takes input variables between installer and uninstaller - nsis

Question

How can I modifiy the below syntax such that my library function can be used in both the installer and the uninstaller? So far I have only managed to find an example for functions that do not take an input value. A good example of which can be found here:
http://nsis.sourceforge.net/Sharing_functions_between_Installer_and_Uninstaller
I haven't been able to work out the syntax should you want to pass varaibles and still utilise the function for both installer and uninstaller.
/* FILE: MyFunctionLibrary.nsh */
Function MyFunction
!define MyFunction"!insertmacro MyFunctionCall"
!macro MyFunctionCall _VAR1
Push "${_VAR1}"
Call MyFunction
!macroend
Exch $0
MessageBox MB_OK $0
Pop $0
FunctionEnd
/* FILE: MyInstallerScript.nsi */
/*...mui setup stuff...*/
!include "MyFunctionLibrary.nsh"
Section Install SEC01
${MyFunction} "install section"
SectionEnd
Section UnInstall SEC02
${MyFunction} "uninstall section"
SectionEnd
/*...other stuff...*/

Answer 1

There are two things going on here. You need to generate both functions and that is often done with a macro. You can also (optionally) provide a helper macro you use to call the function.
The most important step is creating the functions:
; --- MyFunctionLibrary.nsh ---
!macro DeclareMyFunction un
Function ${un}MyFunction
Exch $0
DetailPrint "MyFunction: parameter=$0"
Pop $0
FunctionEnd
!macroend
; --- MyInstallerScript.nsi ---
!insertmacro DeclareMyFunction ""
Section
Push "Hello World"
Call MyFunction
SectionEnd
!insertmacro DeclareMyFunction "un."
Section Uninstall
Push "Hello World"
Call un.MyFunction
SectionEnd
There is also a less common way you can use by providing just the functions code in the macro:
!macro MyFunctionCode
Exch $0
DetailPrint "MyFunction: parameter=$0"
Pop $0
!macroend
Function MyFunction
!insertmacro MyFunctionCode
FunctionEnd
Function un.MyFunction
!insertmacro MyFunctionCode
FunctionEnd
The macro that helps you call the function just needs to perform x number of Push's and Call YourFunction or un.YourFunction:
!macro DeclareMyFunction un
Function ${un}MyFunction
Exch $0
DetailPrint "MyFunction: parameter=$0"
Pop $0
FunctionEnd
!macroend
!define MyFunction "!insertmacro CallMyFunction"
!macro CallMyFunction Param1
Push "${Param1}"
!ifdef __UNINSTALL__
Call un.MyFunction
!else
Call MyFunction
!endif
!macroend
!insertmacro DeclareMyFunction ""
Section
${MyFunction} "Hello World"
SectionEnd
!insertmacro DeclareMyFunction "un."
Section Uninstall
${MyFunction} "Hello World"
SectionEnd
Some of the details can be abstracted away by using util.nsh:
!include Util.nsh
!macro MyFunction
Exch $0
DetailPrint "MyFunction: parameter=$0"
Pop $0
!macroend
!define MyFunction "!insertmacro CallMyFunction"
!macro CallMyFunction Param1
Push "${Param1}"
!insertmacro CallArtificialFunction MyFunction
!macroend
Section
${MyFunction} "Hello World"
SectionEnd
Section Uninstall
${MyFunction} "Hello World"
SectionEnd