How to change defaultdirname parameter just before Install in Inno Setup? - inno-setup

Question

I want to change defaultdirname parameter in ssInstall part. How can I do that? Is there a function for setting [Setup] parameters.

Answer 1

The following global objects are available :
MainForm of type TMainForm, WizardForm of type TWizardForm and UninstallProgressForm of type TUninstallProgressForm and one special constant: crHand of type TControl.Cursor.
If you want to set the default directory in the wizard, just access to it's componants like you would in normal delphi code.
For example, set the directory to a custom value:
WizardForm.DirEdit.Text := 'c:\test';
to read that value you can use the WizardDirValue function.
I say 'just access'... but it took me an hour to figure out ;)

Answer 2

There seems to be no way to change a script constant via scripting.
I think your best bet is to modify the target directory for each entry in the [Files] section, e.g.
[Files]
Source: "MYPROG.EXE"; DestDir: "{code:NewTargetDir}"
and derive your new installation directory like this:
[Code]
function NewTargetDir(Param: String): String;
begin
Result := ExpandConstant('{app}') + '\MySubDir';
end;
Since the NewTargetDir function will be called just before the file is actually copied, this should work.
However, I think you should reconsider your approach. First asking the user to specify a directory to installinto, and then actually installing into a different directory, which seems to be your intent, is the wrong way, IMO. Do you really have a compelling reason to install into another directory than the one specified by the user? Besides, the result of my example code could just as well be achieved by specifying
[Files]
Source: "MYPROG.EXE"; DestDir: "{app}\MySubDir"
without any scripting needed. When in doubt, go for the simpler solution.

Answer 3

I have a similar situation, where the setup app is receiving the install path from the command line.
I'm using the solution proposed by Jonx:
WizardForm.DirEdit.Text := 'c:\test';
Example:
function CompareParameter(param, expected: String): Boolean;
begin
Result := False;
if Length(param) >= Length(expected) then
begin
if CompareText(Copy(param, 1, Length(expected)), expected) = 0 then
begin
Result := True;
end;
end;
end;
function GetParameter(expectedParam: String): String;
var
i : LongInt;
begin
Result := '';
for i := 0 to ParamCount() do
begin
if CompareParameter(ParamStr(i), '/' + expectedParam + '=') then
begin
Result := Copy(ParamStr(i), Length(expectedParam) + 3, Length(ParamStr(i)));
break;
end;
end;
end;
procedure InitializeWizard();
var
newInstallFolder: String;
begin
newInstallFolder := GetParameter('INSTALL_FOLDER');
if Length(newInstallFolder) > 2 then
begin
if Copy(newInstallFolder, 1, 1) = '"' then
newInstallFolder := Copy(newInstallFolder, 2, Length(newInstallFolder) - 2)
if Length(newInstallFolder) > 1 then
WizardForm.DirEdit.Text := newInstallFolder;
end;
end;
The setup app is being started from another setup, in silent mode. It worked OK for me.