delphicleancode Delphi Clean Code — Skill
CRITICAL SKILL — Be concise, direct and solution-focused.
Fundamental Principles
| Principle | Rule |
|---|---|
| SRP | A function/class does ONE thing |
| DRY | Don't repeat code — extract and reuse |
| KISS | Simplest solution that works |
| YAGNI | Don't build what wasn't asked for |
| Boy Scout | Leave the code better than you found it |
Naming Rules (Pascal Guide)
| Element | Convention |
|---|---|
| Variables | Reveal intent: LCustomerCount not N |
| Methods | Verb + noun: GetCustomerById not Customer |
| Booleans | Question form: IsActive, HasPermission, CanEdit |
| Constants | SCREAMING_SNAKE: MAX_RETRY_COUNT |
| Fields | Prefix F: FCustomerName |
| Parameters | Prefix A: ACustomerName |
| Var. locations | Prefix L: LCustomer |
Rule: If you need a comment to explain a name, rename it.
Method Rules
| Rule | Description |
|---|---|
| Short | Maximum 20 lines, ideal 5-10 |
| One Thing | Do one thing and do it well |
| One Level | One level of abstraction per method |
| Few Args | Maximum 3 arguments, prefer 0-2 |
| No Side Effects | Don't mute inputs unexpectedly |
Code Structure
| Standard | Application |
|---|---|
| Guard Clauses | Early returns for edge cases |
| Flat > Nested | Avoid deep nesting (max 2 levels) |
| Composition | Small compound methods |
| Colocation | Related code together |
Guard Clauses in Delphi
//❌ BAD — excessive nesting
procedure ProcessOrder(AOrder: TOrder);
begin
if Assigned(AOrder) then
begin
if AOrder.Items.Count > 0 then
begin
if AOrder.IsValid then
begin
//real logic here
end;
end;
end;
end;
//✅ BOM — guard clauses
procedure ProcessOrder(AOrder: TOrder);
begin
if not Assigned(AOrder) then
raise EArgumentNilException.Create('AOrder cannot be nil');
if AOrder.Items.Count = 0 then
raise EBusinessRuleException.Create('Order must have items');
if not AOrder.IsValid then
raise EValidationException.Create('Order validation failed');
//real logic here — no nesting
end;
Anti-Patterns (DO NOT DO)
| ❌ Pattern | ✅ Fix |
|---|---|
| Comment each line | Delete obvious comments |
| Method > 20 lines | Share by responsibility |
| Magic numbers | Named constants |
with statement |
Explicit local variables |
| Global variables | Constructor injection |
| Generic Catch | Specific exceptions |
Logic in OnClick |
Delegate to Service |
| God class / God unity | One class = one responsibility |
Ignore Free |
try/finally always |
Memory Management
//✅ Temporary objects — always try/finally
LList := TStringList.Create;
try
LList.Add('item');
//use LList
finally
LList.Free;
end;
//✅ Interfaces — reference counting automático
var LService: IMyService;
LService := TMyService.Create; //automatically released
//✅ Owner pattern for visual components
LButton := TButton.Create(Self); //Self frees automatically
AI Code Style
| Situation | Action |
|---|---|
| User requests feature | Write directly |
| User reports bug | Correct, don't explain |
| Requirement unclear | Ask, don't assume |
🔴 Before Editing (THINK FIRST!)
| Question | Why |
|---|---|
| Which units use this? | They can break |
| What does this unit matter? | Interfaces can change |
| What tests cover this? | Tests may fail |
| Is it a shared component? | Multiple points affected |
🔴 Rule: Edit the file + all dependents in the SAME task.
🔴 Self-Check (MANDATORY)
| Check | Pergunta |
|---|---|
| ✅ Goal achieved? | Did I do exactly what was asked? |
| ✅ Edited files? | Have I modified everything necessary? |
| ✅ Does the code work? | Have I tested/verified? |
| ✅ No errors? | Compiles without warnings? |
| ✅ Nothing forgotten? | Edge cases treated? |
| ✅ Memory safe? | Objects released correctly? |
🔴 Rule: If ANY check fails, correct it before finishing.