Check if component was previously downloaded in Inno Setup

Question

I don't know, if, what I'm asking for, it is possible, but anyway, here I go:

I have the following code that uses Inno Download Plugin:

procedure CurPageChanged(CurPageID: Integer);
begin
  if CurPageID = wpReady then
  begin
    idpClearFiles;
    if IsComponentSelected('src') then
    begin
      idpAddFile(
        'https://example.com/files/prj-sources-1.2.3.zip',
        ExpandConstant('{tmp}\src.zip'));
    end;
  end;
end;

and I would like to check, if the file is already downloaded in a folder before downloading it again, and if it is not, to download it.

Answer 1

You can check whether the file exists by the FileExists function. In your case it would be like:

procedure CurPageChanged(CurPageID: Integer);
var
  FileName: string;
begin
  if CurPageID = wpReady then
  begin
    idpClearFiles;
    { better use a local variable to avoid expanding the same path twice }
    FileName := ExpandConstant('{tmp}\src.zip');
    { if the component item is checked and file does not exist yet, enqueue it }
    if IsComponentSelected('src') and not FileExists(FileName) then
    begin
      idpAddFile(
        'https://example.com/files/prj-sources-1.2.3.zip',
        FileName);
    end;
  end;
end;