Harnessing the Power of .RC and .RES Files in Delphi: A Comprehensive Guide

Delphi empowers developers to create robust applications with ease. While building applications, it's crucial to manage resources efficiently, and that's where .rc (resource script) and .res (compiled resource) files come into play. In this blog post, we'll explore their usage in a Delphi project, focusing on creating a simple non-visual component and discussing two common approaches for handling resource files.

Understanding .RC and .RES Files

What are .RC Files?

Resource scripts (.rc files) are text files that contain a set of instructions and definitions describing resources for an application. These resources can include icons, bitmaps, strings, dialogs, and more. In Delphi, .rc files are commonly used to manage resources and provide a centralized way to organize them.

The Role of .RES Files

When you compile an .rc file, it generates a compiled resource file (.res). The .res file contains binary data representing the resources specified in the .rc file. This compiled format is more efficient for runtime loading and improves the overall performance of the application.

Scenario: Creating a Simple Non-Visual Component

Let's dive into a practical example by creating a simple non-visual component in Delphi and managing resources for it.

Step 1: Creating the Delphi Component

unit SimpleComponent;

interface

uses
  System.Classes;

type
  TSimpleComponent = class(TComponent)
  private
    FMessage: string;
  public
    constructor Create(AOwner: TComponent); override;
    procedure ShowMessage;
  published
    property Message: string read FMessage write FMessage;
  end;

implementation

uses
  Vcl.Dialogs;

constructor TSimpleComponent.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FMessage := 'Hello, Delphi!';
end;

procedure TSimpleComponent.ShowMessage;
begin
  ShowMessage(FMessage);
end;

end.

Step 2: Adding Resources from the Project Menu

1. Open your Delphi project.

2. Navigate to Project -> Resources and Images -> Add -> New -> Resource Type: `STRING`, Name: `MY_MESSAGE`.

3. Set the value of `MY_MESSAGE` to your desired message, e.g., "Greetings from Resource".

Step 3: Using the Resource in Delphi Code

unit SimpleComponent;

interface

uses
  System.Classes;

type
  TSimpleComponent = class(TComponent)
  private
    FMessage: string;
  public
    constructor Create(AOwner: TComponent); override;
    procedure ShowMessage;
  published
    property Message: string read FMessage write FMessage;
  end;

implementation

uses
  Vcl.Dialogs, System.SysUtils, System.StrUtils;

{$R *.dfm} // Ensure that this line is present

constructor TSimpleComponent.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);

  // Access the resource string
  FMessage := LoadStr({Resource ID});
end;

procedure TSimpleComponent.ShowMessage;
begin
  ShowMessage(FMessage);
end;

end.

Step 4: Compiling .RC with Command Line

1. Create a new text file named `SimpleComponent.rc`:

MY_MESSAGE STRING "Greetings from Command Line Resource"

2. Open the command prompt and navigate to the folder containing the .rc file.

3. Compile the .rc file using the `BRCC32` compiler:

BRCC32 SimpleComponent.rc

4. Ensure that the generated `SimpleComponent.res` file is present.

Step 5: Using Command Line Resource in Delphi Code

unit SimpleComponent;

interface

uses
  System.Classes;

type
  TSimpleComponent = class(TComponent)
  private
    FMessage: string;
  public
    constructor Create(AOwner: TComponent); override;
    procedure ShowMessage;
  published
    property Message: string read FMessage write FMessage;
  end;

implementation

uses
  Vcl.Dialogs, System.SysUtils, System.StrUtils;

{$R SimpleComponent.res} // Include the compiled resource file

constructor TSimpleComponent.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);

  // Access the resource string
  FMessage := LoadStr({Resource ID});
end;

procedure TSimpleComponent.ShowMessage;
begin
  ShowMessage(FMessage);
end;

end.

Conclusion

In this blog post, we explored the significance of .rc and .res files in Delphi projects. By creating a simple non-visual component, we demonstrated two approaches for managing resources—adding them from the project menu and compiling an .rc file using the command line. Efficient resource management is crucial for building robust Delphi applications, and understanding the use of .rc and .res files is a key step toward achieving that goal.