Payoo iOS Code Review

Comprehensive code review for the Payoo Merchant iOS app following Clean Architecture with RxSwift and Swinject.

When to Activate

• "review code", "check code", "code review"
• "review PR", "review pull request", "check pull request"
• "review this file", "check this ViewModel"
• "is this code correct", "any issues with this code"
• When analyzing Swift files in PayooMerchant, Domain, Data, or Analytics layers

Review Process

Step 1: Identify Scope

• Single file review → Read the file
• Multiple files → Use Glob to find related files
• Pull request → Check git diff for changed files
• Full feature → Grep for related ViewModels/UseCases

Step 2: Layer-Specific Checks

For Presentation Layer (PayooMerchant/)

1. MVVM Pattern

   • ✓ ViewModel implements ViewModelType protocol
   • ✓ Has Input and Output nested types
   • ✓ Has transform(input:) -> Output method
   • ✓ ViewControllers bind to Input/Output only
   • ✓ No business logic in ViewControllers

2. RxSwift Memory Management

   • ✓ Every ViewController/ViewModel has DisposeBag
   • ✓ All subscriptions use .disposed(by: disposeBag)
   • ✓ Closures capturing self use [weak self] or [unowned self]
   • ✓ No retain cycles in Observable chains

3. Navigation & DI

   • ✓ Navigator passed as dependency (never created directly)
   • ✓ UseCases injected via constructor
   • ✓ No direct ViewController instantiation
   • ✓ Uses factory methods from ViewControllerFactory

4. Session Error Handling

   • ✓ CRITICAL: All API calls have .catchSessionError(sessionUC)
   • ✗ Missing .catchSessionError() → Session timeout won't logout

For Domain Layer (Domain/)

1. Clean Architecture Rules

   • ✓ Pure Swift only (no UIKit imports)
   • ✓ No imports from Data or Presentation layers
   • ✓ Only protocols for services (no implementations)
   • ✓ Models are simple structs/classes

2. UseCase Pattern

   • ✓ Protocol defines interface (UseCaseType)
   • ✓ Implementation injected with dependencies
   • ✓ Single responsibility per UseCase
   • ✓ Returns RxSwift Observables/Singles/Maybes
   • ✓ Uses .catchSessionError(sessionUC) for API calls

3. Service Protocols

   • ✓ Defined in Domain/Service/
   • ✓ Implemented in Data layer
   • ✓ Injected via Swinject

For Data Layer (Data/)

1. Repository Pattern

   • ✓ Implements Domain service protocols
   • ✓ Uses Moya for network calls
   • ✓ Uses Realm for local storage
   • ✓ Converters transform DTOs ↔ Domain models

2. API Models

   • ✓ DTOs in Data/Model/
   • ✓ Conform to DomainConvertible or RealmRepresentable
   • ✓ Use ObjectMapper for JSON parsing
   • ✓ Don't leak to Domain/Presentation layers

Step 3: Project-Wide Checks

1. SwiftLint Compliance

   • Run: ./Pods/SwiftLint/swiftlint lint --reporter xcode
   • Check: Type body length (300/400), file length (800/1200)
   • Check: Opt-in rules (empty_count, yoda_condition, todo, etc.)

2. Common Pitfalls

   • Missing .catchSessionError() on API observables
   • Manual ViewController instantiation (should use factory)
   • Missing DependencyContainer registration
   • Breaking layer boundaries (e.g., Data imported in Domain)
   • Missing disposed(by: disposeBag)
   • Strong self in closures causing retain cycles
   • Using .count > 0 instead of .isEmpty (SwiftLint)
   • Force unwraps without justification
   • Magic numbers without constants

3. RxSwift Best Practices

   • Use Driver for UI bindings (never fails, main thread)
   • Use Single for one-time operations (network calls)
   • Use Observable for streams
   • Use Maybe for optional single values
   • Prefer .bind(to:) over .subscribe(onNext:)

4. Naming Conventions

   • ViewModels: [Feature]ViewModel (e.g., LoginViewModel, TransactionHistoryViewModel)
   • ViewControllers: [Feature]ViewController (e.g., LoginViewController)
   • UseCases: [Action]UseCase (e.g., GetProfileUseCase, LoginUseCase)
   • UseCase protocols: [Action]UseCaseType (e.g., GetProfileUseCaseType)
   • Navigators: [Feature]Navigator (e.g., LoginNavigator, HomeNavigator)
   • Navigator protocols: [Feature]NavigatorType
   • Services (protocols): [Name]Service (e.g., ApiService, LocalStorageService)
   • Services (impl): Default[Name]Service or [Tech][Name]Service (e.g., DefaultApiService, RealmStorageService)
   • Protocols: [Name]Type suffix for main protocols
   • Variables: camelCase, descriptive (avoid abbreviations like usrNm, use username)
   • Constants: camelCase for local, or k prefix for global (e.g., kMaxRetryCount)
   • IBOutlets: Descriptive names with type suffix (e.g., loginButton, usernameTextField)
   • Avoid single letters except in loops (i, j) or common conventions (x, y)

Step 4: Generate Report

Format:

## Code Review: [File/Feature Name]

### 📋 Summary
Files: X | 🔴 Critical: X | 🟡 Warning: X | 🔵 Info: X | Status: [✅ Approved / ⚠️ Needs fixes / ❌ Blocked]

### ✅ Strengths
- [List good patterns found]

### ⚠️ Issues Found

#### 🔴 Critical (Must Fix)
**[Issue]** at [file:line]
- **Problem**: [Description]
- **Impact**: [Why critical]
- **Fix**:
\`\`\`swift
// Corrected code
\`\`\`

#### 🟡 Warning (Should Fix)
**[Issue]** at [file:line]
- **Problem**: [Description]
- **Suggestion**: [How to fix]

#### 🔵 Info (Consider)
**[Issue]** at [file:line]
- **Note**: [Observation]
- **Suggestion**: [Optional improvement]

Review Categories

Critical Issues (Must Fix)

• Missing .catchSessionError() on API calls
• Retain cycles / memory leaks
• Breaking Clean Architecture layer boundaries
• Missing DisposeBag disposal
• Force unwraps in unsafe contexts

Warnings (Should Fix)

• Manual ViewController instantiation
• Missing DependencyContainer registration
• SwiftLint violations
• Non-descriptive variable names
• Large type bodies (>300 lines)

Info (Consider)

• Potential optimizations
• Code duplication
• Missing unit tests
• Outdated comments
• TODO/FIXME comments

Quick Commands

Run SwiftLint:

./Pods/SwiftLint/swiftlint lint --reporter xcode

Find files without DisposeBag:

grep -L "DisposeBag" PayooMerchant/**/*ViewModel.swift

Find API calls without catchSessionError:

grep -r "apiService\." --include="*.swift" | grep -v "catchSessionError"

Example Review Flow

1. User: "Review LoginViewModel"
2. Read PayooMerchant/Controllers/Login/LoginViewModel.swift
3. Check MVVM pattern, RxSwift, DI
4. Grep for related files (LoginViewController, LoginUseCase)
5. Run SwiftLint on the file
6. Generate detailed report with line numbers
7. Provide fix recommendations

Key Architectural Rules

1. Layer Dependencies

   Presentation → Domain ← Data
   

   • Presentation can import Domain
   • Data can import Domain
   • Domain imports nothing (pure Swift)
   • NEVER: Domain imports Data/Presentation

2. RxSwift Pattern

   // ViewModel transform pattern
   func transform(input: Input) -> Output {
       let result = input.trigger
           .flatMapLatest { [weak self] _ -> Observable<Data> in
               guard let self = self else { return .empty() }
               return self.useCase.execute()
                   .catchSessionError(self.sessionUC) // CRITICAL!
           }
       return Output(result: result.asDriver(onErrorJustReturn: .empty))
   }
   

3. Memory Management

   // CORRECT
   .subscribe(onNext: { [weak self] value in
       self?.updateUI(value)
   }).disposed(by: disposeBag)
   
   // WRONG - Retain cycle!
   .subscribe(onNext: { value in
       self.updateUI(value)
   }).disposed(by: disposeBag)
   

Output Format

Always provide:

1. Clear issue categorization (Critical/Warning/Info)
2. File paths with line numbers for clickable links
3. Code snippets showing the problem
4. Concrete fix recommendations
5. Summary with metrics

Reference: See standards.md for detailed coding standards and examples.md for review examples.