How to set my own variable in [Setup] and read it from [Code]

I'm trying to create a script in Inno Setup to pull files from a GitHub repository, extract it, and write it to a directory defined in the [Setup] section.

[Setup]
MyVariable={userappdata}\MetaQuotes\Terminal\{#MyAppName}

[Code]
procedure CurStepChanged(CurStep: TSetupStep);
begin
  // Copy the selected files to the selected directory
  if not FileCopy(Output + '\file1.txt', MyVariable + '\file1.txt', False) then
  begin
    MsgBox('Failed to copy file1.txt to the selected directory.', mbError, MB_OK);
    Abort();
  end;
  if not FileCopy(Output + '\file2.txt', MyVariable + '\file2.txt', False) then
  begin
    MsgBox('Failed to copy file2.txt to the selected directory.', mbError, MB_OK);
    Abort();
  end;
end;

Obviously, this won't compile because MyVariable hasn't been defined in the Pascal script. Only, I'm not sure how to reference the value in [Setup]. Or am I going about this in the wrong way?

Solution

Well, you can read the [Setup] section directives with SetupSetting preprocessor function:
How to read a [Setup] parameter in the Pascal code?

But you cannot invent your own new directives.

But you can either:

Use preprocessor variable using #define directive (the way you already use it for MyAppName):
```
#define MyVariable "{userappdata}\MetaQuotes\Terminal\" + MyAppName
```
It does not matter where you place the #define as long as it it before you use the variable.

Use it like this in the Pascal Script:
```
ExpandConstant('{#MyVariable}\file1.txt')
```
The ExpandConstant is to expand the {userappdata}.

Use Pascal Script constant:

[Code]

const 
  MyVariable = '{userappdata}\MetaQuotes\Terminal\{#MyAppName}';

Use it like any other Pascal Script variable/constant.

ExpandConstant(MyVariable) + '\file1.txt'