HelpNDoc脚本构建失败，报错Unknown name 'aList' 原因是什么？

你编写的用于导出HelpNDoc主题信息的Pascal脚本如下：

const
  // Define the output file
  OUTPUT_FILE = 'd:\topics.txt';

var
  // Current topic ID
  aTopicId: string;
  // List of output
  aList: TStringList;

begin
  // Init list
  aList := TStringList.Create;
  aList.Add('Topic Caption | Help ID | Help Context | Meta Description');
  try
    // Get first topic
    aTopicId := HndTopics.GetTopicFirst();
    // Loop through all topics
    while aTopicId <> '' do
    begin
      // Add the topic to the list
      aList.Add(Format('%s | %s | %d | %s', [
        HndTopics.GetTopicCaption(aTopicId),
        HndTopics.GetTopicHelpId(aTopicId),
        HndTopics.GetTopicHelpContext(aTopicId),
        HndTopics.GetTopicDescription(aTopicId)        
      ]));
      // Get next topic
      aTopicId := HndTopics.GetTopicNext(aTopicId);
    end;
    // Create the file
    aList.SaveToFile(OUTPUT_FILE);
  finally
    aList.Free;
  end;
end.

运行时出现的错误提示：

[Error] script(9, 3): Unknown name "aList"

错误原因 #

HelpNDoc的脚本引擎基于Delphi语言子集，但默认并未自动引入TStringList所属的Classes单元。在标准Delphi环境中，TStringList类定义在Classes.pas单元内，若脚本中未显式声明引用该单元，脚本引擎会无法识别TStringList类型，进而导致变量aList被判定为未定义的未知名称。

解决方法 #

在脚本开头的const声明前添加uses Classes;，显式引入包含TStringList的单元，修改后的脚本如下：

uses Classes;

const
  // Define the output file
  OUTPUT_FILE = 'd:\topics.txt';

var
  // Current topic ID
  aTopicId: string;
  // List of output
  aList: TStringList;

begin
  // Init list
  aList := TStringList.Create;
  aList.Add('Topic Caption | Help ID | Help Context | Meta Description');
  try
    // Get first topic
    aTopicId := HndTopics.GetTopicFirst();
    // Loop through all topics
    while aTopicId <> '' do
    begin
      // Add the topic to the list
      aList.Add(Format('%s | %s | %d | %s', [
        HndTopics.GetTopicCaption(aTopicId),
        HndTopics.GetTopicHelpId(aTopicId),
        HndTopics.GetTopicHelpContext(aTopicId),
        HndTopics.GetTopicDescription(aTopicId)        
      ]));
      // Get next topic
      aTopicId := HndTopics.GetTopicNext(aTopicId);
    end;
    // Create the file
    aList.SaveToFile(OUTPUT_FILE);
  finally
    aList.Free;
  end;
end.

内容的提问来源于stack exchange，提问作者Andrew Truckle