Better way to display [error] messages

Problem/Question/Abstract:

Better way to display [error] messages

Answer:

If you display more than a few [error] messages in your application, using a simple method such as the following may not be the best approach:

Application.MessageBox('File not found', 'Error', mb_OK);

Above method of displaying errors will make it harder to modify actual messages since they are distributed all over your application source code. It may be better to have a "centralized" function that can display error messages, or better yet, a centralized function that can display replaceable error messages. Consider the following example:

type
  cnMessageIDs =
    (
    nMsgID_NoError,
    nMsgID_FileNotFound,
    nMsgID_OutOfMemory,
    nMsgID_ExitProgram
    // list your other error
    // IDs here...
    );

const
  csMessages_ShortVersion: array[Low(cnMessageIDs)..High(cnMessageIDs)] of PChar =
  (
    'No error',
    'File not found',
    'Out of memory',
    'Exit program?'
    // other error messages...
    );

  csMessages_DetailedVersion: array[Low(cnMessageIDs)..High(cnMessageIDs)]
  of PChar =
    (
    'No error; please ignore!',

    'File c:\config.sys not found.' +
    'Contact your sys. admin.',

    'Out of memory. You need ' +
    'at least 4M for this function',

    'Exit program? ' +
    'Save your data first!'
    // other error messages...
    );

procedure MsgDisplay(
  cnMessageID: cnMessageIDs);
begin
  // set this to False to display
  // short version of the messages
  if (True) then
    Application.MessageBox(csMessages_DetailedVersion[cnMessageID], 'Error', mb_OK)
  else
    Application.MessageBox(csMessages_ShortVersion[cnMessageID], 'Error', mb_OK);
end;

Now, whenever you want to display an error message, you can call the MsgDisplay() function with the message ID rather than typing the message itself:

MsgDisplay(nMsgID_FileNotFound);

MsgDisplay() function will not only let you keep all your error messages in one place -- inside one unit for example, but it will also let you keep different sets of error messages -- novice/expert, debug/release, and even different sets for different languages.