delphi-pascal

Skill: delphi-pascal

Cursor Agent-Requested Rule — applied when AI determines relevance.

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Delphi & Pascal Development

Patterns and practices for Object Pascal / Delphi development.

When to Use This Skill

• Building Windows desktop applications with VCL or FireMonkey (FMX)
• Maintaining or modernizing legacy Delphi/Pascal codebases
• Cross-platform development with Delphi (Windows, macOS, Linux, mobile)
• Database applications with FireDAC or dbExpress
• REST/JSON API development with Delphi

Modern Delphi Best Practices

Project Structure

MyProject/
├── src/
│   ├── Main.dpr           # Project file
│   ├── Forms/             # UI forms
│   │   ├── MainForm.pas
│   │   └── MainForm.dfm
│   ├── DataModules/       # Data access
│   │   └── dmMain.pas
│   ├── BusinessLogic/     # Domain logic
│   │   └── UserService.pas
│   └── Utils/             # Helpers
│       └── CryptoUtils.pas
├── tests/
│   └── DUnitX/
└── packages/              # Custom components

Naming Conventions

Type	Prefix	Example
Type	T	TUser
Class ref	Class	TUserClass
Interface	I	IUserService
Record	T	TPoint
Enum	T	TColorScheme
Enum value	2-letter	csDark
Field	F	FUserName
Parameter	A	AUserName
Local var	L	LResult
Unit	2-letter prefix	uUserService
Form	Form	frmMain
DataModule	dm	dmDatabase
Component	Type prefix	btnSave, edtName, grdUsers

Error Handling

// ✅ GOOD - Proper exception handling
try
  Connection.Open;
  Query.Execute;
except
  on E: EDatabaseError do
  begin
    Log.Error('Database error: %s', [E.Message]);
    raise EServiceException.CreateFmt('Service unavailable: %s', [E.Message]);
  end;
end;

// ❌ BAD - Swallowing exceptions
try
  DoSomething;
except
  // silent failure
end;

Memory Management

// ✅ GOOD - RAII pattern with interfaces
var
  Service: IService;
begin
  Service := TService.Create;
  Service.Process;  // Auto-freed when Service goes out of scope
end;

// ✅ GOOD - Try-finally for objects
var
  Stream: TFileStream;
begin
  Stream := TFileStream.Create('file.dat', fmCreate);
  try
    Stream.WriteBuffer(Data, SizeOf(Data));
  finally
    Stream.Free;
  end;
end;

// ❌ BAD - No cleanup
var
  Obj: TObject;
begin
  Obj := TObject.Create;
  Obj.DoSomething;
  // Memory leak!
end;