Al-Muhandis / QTemplate

Object Pascal's quick templating engine

QTemplate - Object Pascal's quick templating engine

This unit implements an alternative to FPTemplate engine, with different approach. FPTemplate uses event driven approach where a the core lies in OnReplaceTag callback. For example, consider the following template:

{+MyTag [Param1=Value1] [Param2=Value2]+}

An example OnReplaceTag callback:

procedure TMyTemplateHandler.MyReplaceTag(
        Sender      : TObject;
  const TagString   : String;
        TagParams   : TStringList;
  out   ReplaceText : String
);
begin
  (*
    Here, the parameter values are:
    TagString = 'MyTag'
    TagParams = [
      'Param1' = 'Value1'
      'Param2' = 'Value2'
    ]
  *)
  // Common implementation
  if TagString = 'MyTag' then begin
    // do replacement for MyTag
    ReplaceText := ... ;
  end else if TagString = ... begin
    // do replacement for other tag
  end else if TagString = ... begin
    // do replacement for other tag
  end else begin
    // not a recognized tag
  end;
end;

As you can see, a series of if statement must be implemented. This could get messy for template with a lot of tags. QTemplate removes above burden to check for tag and instead gives a nice and easy to use map like functionality to connect tag and callback. QTemplate way to solve above case is:

function TMyTemplateHandler.ReplaceMyTag(const ATag: String; AParams: TStringList): String;
begin
  
end;

function TMyTemplateHandler.ReplaceMyOtherTag(const ATag: String; AParams: TStringList): String;
begin
  
end;

then somewhere (constructor is a good choice):

begin
  with TQTemplate.Create('templatefilename') do
    try
      Tags['MyTag'] := @ReplaceMyTag;
      Tags['MyOtherTag'] := @ReplaceMyOtherTag;
      { you may have same handler for a tag handling that differs a little, hence the idea
        of ATag parameter in the callback }
      Tags['MySomeOtherTag'] := @ReplaceMyOtherTag;
      WriteOutput(GetContent);
    finally
      Free;
    end;
end;