I'm using Inno Setup to create an installer.
I want the installer to automatically uninstall the previous installed version, instead of overwriting it. How can I do that?
I have used the following. I'm not sure it's the simplest way to do it but it works.
This uses {#emit SetupSetting("AppId")}
which relies on the Inno Setup Preprocessor. If you don't use that, cut-and-paste your App ID in directly.
[Code]
{ ///////////////////////////////////////////////////////////////////// }
function GetUninstallString(): String;
var
sUnInstPath: String;
sUnInstallString: String;
begin
sUnInstPath := ExpandConstant('Software\Microsoft\Windows\CurrentVersion\Uninstall\{#emit SetupSetting("AppId")}_is1');
sUnInstallString := '';
if not RegQueryStringValue(HKLM, sUnInstPath, 'UninstallString', sUnInstallString) then
RegQueryStringValue(HKCU, sUnInstPath, 'UninstallString', sUnInstallString);
Result := sUnInstallString;
end;
{ ///////////////////////////////////////////////////////////////////// }
function IsUpgrade(): Boolean;
begin
Result := (GetUninstallString() <> '');
end;
{ ///////////////////////////////////////////////////////////////////// }
function UnInstallOldVersion(): Integer;
var
sUnInstallString: String;
iResultCode: Integer;
begin
{ Return Values: }
{ 1 - uninstall string is empty }
{ 2 - error executing the UnInstallString }
{ 3 - successfully executed the UnInstallString }
{ default return value }
Result := 0;
{ get the uninstall string of the old app }
sUnInstallString := GetUninstallString();
if sUnInstallString <> '' then begin
sUnInstallString := RemoveQuotes(sUnInstallString);
if Exec(sUnInstallString, '/SILENT /NORESTART /SUPPRESSMSGBOXES','', SW_HIDE, ewWaitUntilTerminated, iResultCode) then
Result := 3
else
Result := 2;
end else
Result := 1;
end;
{ ///////////////////////////////////////////////////////////////////// }
procedure CurStepChanged(CurStep: TSetupStep);
begin
if (CurStep=ssInstall) then
begin
if (IsUpgrade()) then
begin
UnInstallOldVersion();
end;
end;
end;
Alternatives
See also this blog post "Inno Setup Script Sample for Version Comparison" which goes one step further, and reads the version number of any previously installed version, and compares that version number with that of the current installation package.