Delphi - Component Naming Conventions / Branding

I discuss programming naming conventions elsewhere. This page discusses how to name objects and components you create. In general, you should add a 2- or 3-letter prefix to the code you generate that identifies who you are. Frequently, this will identify your company. Besides simply branding your work, the main purpose of this is to reduce naming conflicts.

Some of the newer languages require the name of the library (object file) be typed before every instance of a function defined in the library.

log(x)    vs    math.log(x)

Thankfully, Delphi 5 does not require that nonsense .. but it does allow it when 2 units (the Delphi version of libraries and object files) contain items with the same name.

Over a number of years, I have come up with *a* scheme for naming things that I plan to reuse in multiple projects.

Some of my older code does not follow these guidelines.

The Problem | Units | Global Constants and Functions | Object Names | Single Global Objects

The Problem

Delphi does not allow a unit and a global identifier (variable, function, object, ...) to have the same name. This is necessary because any global identifier can be qualified by the name of the unit it is defined in. When a unit (file) simply defines types, this is not a problem - you simply prefix the unit name with the letter 'T'.

Unit     xxSomename
object  TxxSomename = class ...

The problem arises when the unit also defines a global instance of the object .. and I want all 3 names to be similar. In those cases, I prefer to add an underscore between the branding identifier and the object identifier.

Unit     xxSomename
object  Txx_Somename = class ...
var      xx_Somename : Txx_Somename;

I tried placing the underscore after the 'T'.

Unit     xxSomename
object T_xxSomename = class ...

However, when the component is placed on a form, Delphi creates the default name by dropping the initial-T and adding a number.

type
  TForm1 = class(TForm)
    _xxSomename1: T_xxSomename; // Starts with an underscore
  private

and I don't want variable names to start with an underscore.

However, I always use an underscore before a trailing branding identifier. See Global Constants and Functions (below) for examples.

Units

Most languages provide a way to package code so that it is relatively easy to use it in multiple programs. The terminology and specifics vary from one language to another, but the general purpose is the same.

Language	Package Name	Comment
Delphi	Unit	A combination of the c-style object files and the c-style header files
C++	Object	Compiled files, ready to be linked. Requires a separate header file.
Java	Library	Partially compiled Class files
Action Script 3	Package	Text files in a well defined directory structure - The package name is the directory path.

The Delphi unit is compiled from several source files - all of which have the same name, but different extensions. This is the name that must be included in the Uses clause.

While it is possible to distribute units (name.dcu) without any source, Delphi has made this difficult. Unfortunately, a different version of the dcu file is required for each version of Delphi.

I name the units by using a 2-letter prefix.

unit mcCommon;

mcCommon.pas  Source file
mcCommon.dcu  Delphi Compiled Unit

Global Constants and Functions

For constants, and many global functions, I use a suffix.

from mcCommon.pas

const
    // These "end" in "_mc" to make them easier to find in the help
  CRLF_mc = #13#10 ;  // CR/LF - Carriage Return/Linefeed
  CR_mc   = #13;      // CR    0Dh    #$0D
  LF_mc   = #10;      // LF    0Ah

  function   Left_mc (s: string; NumOfCharacters : integer):string; overload;
  function  Right_mc (s: string; NumOfCharacters : integer):string; overload;

From unit mcExtras, sometimes I use a prefix.

procedure mc_CopyText_and_Formating(Src, Dest: TRichEdit{TCustomMemo});

procedure mc_SetCaretPos(Memo:TCustomMemo; Line: integer; Char: integer=0);

function  mc_DateTime_to_24hr(DateTime: string='now'): string; overload;

I use the suffix styling when I am more likely to type something logical and want the built-in help to suggest appropriate options, and the prefix styling for more complicated names.

Object Names

Typically, I will use a prefix for object names. (A component is simply an object that can be selected from a toolbar.)

Single Global Objects

There are many times that I want a single, globally available object. For these, I prefer the mc_ styling.

From unit mcExtras,


type Tmc_File_Version_Info = class
  private
  public
    constructor Create; virtual;

     // the details don't matter on this page

end;

function  mc_File_Version_Info: Tmc_File_Version_Info;

implementation

var
  Fmc_File_Version_Info : Tmc_File_Version_Info;


function  mc_File_Version_Info: Tmc_File_Version_Info;
begin
  if Fmc_File_Version_Info=nil then begin
    Fmc_File_Version_Info := Tmc_File_Version_Info.Create;
  end;

  result := Fmc_File_Version_Info;
end;

{ end mc_File_Version_Info }

initialization  // required so that *finalization* can be defined

finalization
  Fmc_File_Version_Info.Free;

mc_LogFiles is one of the exceptions. In this case, I placed the underscore in the unit name / filename and used a global variable (instead of a function) to access it.

unit mc_LogFiles;

type
  Tmc_LogFiles = class(TObject)
     // the details don't matter on this page
  end;

var
  mcLogFiles: Tmc_LogFiles;

implementation

initialization
  mcLogFiles := Tmc_LogFiles.Create ;

finalization
  mcLogFiles.Free;

I haven't decided which method to access the object is "best", but I have decided to use the underscore for the objects and to omit it for the class.

Author: Robert Clemenzi