The problem that I had

Let’s say that I have my_app_installer which contains the following files:

my_app_installer			<-- created using InstallShield 2016
  ├── app_files				<-- expected to be installed on "A location"
  └── metadata_file			<-- will be installed on "B location"

metadata_file contains my app info and install location (“A location”) and the only reference used by other_apps to get the metadata info.

The problem started when the user installed my_app_installer into “C location” (where the app_files are being extracted). Not in “A location” as I expected. This will cause other_apps are unable to recognize the installation of my app because they only use my metadata_file to acquire the metadata info and also install location.

The solution that I used to fix it

To solve this problem, I figured it out that I need to apply a deferred custom action using InstallScript. The reason for using the deferred custom action is because I need to make a change to the system and only the deferred custom action can be run in elevated context. Meaning after the installation of my app_files is completed, the deferred custom action will find my metadata_file and replace A location info with C location info.

Here’s how I did it in InstallShield 2016:

1. Created New Set Property custom action (type 51)

• Custom action name: CA_PopulateCustomActionData
• Property Name: CA_UpdateMetadataFile
• Property Value: [INSTALLDIR]
• Install Exec Sequence: After ScheduleReboot
• Install Exec Condition: NOT REMOVE

The purpose of this type-51 custom action is to pass other property value to CustomActionData property since the deferred custom action can only access to these built-in Windows Installer properties; CustomActionData, ProductCode and UserSID. That is the limitation of the deferred custom action.

2. Created New InstallScript custom action as a deferred custom action

• Custom action name: CA_UpdateMetadataFile
• Function Name: MODIFY_METADATA
• In-Script Execution: Deferred Execution
• Install Exec Sequence: After CA_PopulateCustomActionData
• Install Exec Condition: NOT REMOVE

Below is the InstallScript that I used to associate with my deferred custom action as defined above:

#include "ifx.h"
#include "isrt.h"
#include "iswi.h"

prototype FindAndReplace(STRING, STRING, STRING);

//Global Variables
STRING SrcDirFileName, SrchString, RplcString;
STRING firstPart;
NUMBER SrchLen, nvLineNumber;

function FindAndReplace(SrcDirFileName, SrchString, RplcString)
	STRING svReturnLine,szString, secPart;
	NUMBER nReturn, subPos;
begin
	Disable(STATUSEX); //stop displaying the progress bar
    ShowObjWizardPages(NEXT); //WARNING this may throw a user interface
    SrchLen = StrLength(SrchString); //length of search string
    nvLineNumber = 0; //pre-set file line number to 0
    
    Din: 
		while (FileGrep (SrcDirFileName, SrchString, svReturnLine, nvLineNumber, RESTART)=0)
			//subPos is the number where the first char of search string was found
			subPos	= StrFind(svReturnLine, SrchString);
			//firstPart is the string upto search string but not including searchString
			StrSub (firstPart, svReturnLine, 0, subPos);
			//secPart is the string after search string
			StrSub (secPart, svReturnLine, subPos+SrchLen, 50);
			//new string is firstPart followed by replace string followed by secPart
			TextSub.Value( "SUBBED" ) = RplcString;
			szString = firstPart+"<SUBBED>"+secPart;
			TextSub.Substitute( szString );
			//write line replacing original  
			FileInsertLine (SrcDirFileName, szString, nvLineNumber, REPLACE);
			//the code below examines the line written back for any other occurences
			//systematically searching and re-writting back to file
			//search first line again for search string
			if (FileGrep (SrcDirFileName, SrchString, svReturnLine, nvLineNumber, RESTART)=0) then
				goto Din;  //another occurence found
			else
				//increment line number and start all over again
				nvLineNumber = nvLineNumber + 1;
			endif;
		endwhile;  //while loop exited when END_OF_FILE reached  
end;

export prototype MODIFY_METADATA(HWND);
function MODIFY_METADATA(hMSI)
	STRING installDirPath;
	NUMBER installDirPathBuffer;
begin
	installDirPathBuffer = MAX_PATH;
	if (MsiGetProperty(hMSI, "CustomActionData", installDirPath, installDirPathBuffer) == ERROR_SUCCESS) then
		StrReplace(installDirPath,"\\","\\\\",0);
	endif;
	if (SYSINFO.bIsWow64 != 0) then
		if Is(FILE_EXISTS, "<PATH_TO_METADATA_FILE>") = TRUE then
			FindAndReplace("<PATH_TO_METADATA_FILE>","<STRING_TO_FIND>", installDirPath);
		endif;
	else
		if Is(FILE_EXISTS, "<PATH_TO_METADATA_FILE>") = TRUE then
			FindAndReplace("<PATH_TO_METADATA_FILE>","<STRING_TO_FIND>", installDirPath);
		endif;
	endif;
end;

The script above should be self-explanatory. If you encountered the similar problem as mine, you may need to change <PATH_TO_METADATA_FILE> and <STRING_TO_FIND> to your own strings. Be aware of possible deadlock, if any, you may need to apply certain conditional statement (checking). Hopefully this method may help others who are in the similar situation.