# CHAPTER 7 SUMMARY

## Key Concepts Introduced
1. **TypeScript Integration** - Compile-time type safety - Used in chapters: 8, 10, 13, 14
2. **Runtime Type Inference** - Learning types from responses - Used in chapters: 10, 12
3. **OpenAPI Auto-Discovery** - Automatic type generation - Used in chapters: 13
4. **Type Validation** - Runtime checking with detailed errors - Used in chapters: 10, 12
5. **Type Guards** - Runtime type checking functions - Used in chapters: 10, 13
6. **Discriminated Unions** - Safe handling of different shapes - Used in chapters: 10
7. **Generic API Clients** - Reusable typed patterns - Used in chapters: 13, 14
8. **Type Transformation** - Converting API types to app types - Used in chapters: 8, 10
9. **Branded Types** - Extra type safety for IDs - Used in chapters: 13
10. **Type Generation** - Export learned/discovered types - Used in chapters: 13

## Code Patterns Established
```typescript
// Pattern 1: Manual types
const { data } = await tf.get<User>('/api/users/123')

// Pattern 2: Runtime inference
tf.configure({ inference: { enabled: true } })
const typeInfo = tf.getTypeInfo('/api/users/*')

// Pattern 3: OpenAPI discovery
await tf.discover('https://api.example.com')

// Pattern 4: Type validation
const { data, valid, errors } = await tf.get<User>(url, {
  validate: true
})

// Pattern 5: Type guards
function isUser(obj: unknown): obj is User {
  return typeof obj === 'object' && 'id' in obj
}
```

## Advanced Patterns Introduced
1. **Progressive Type Learning** - Build confidence over samples
2. **Pattern Detection** - Recognize email, URL, date formats
3. **Enum Detection** - Find enum-like fields automatically
4. **Optional Field Detection** - Track which fields are optional
5. **Type Export** - Generate TypeScript definitions
6. **API Exploration** - Crawl APIs to discover types

## Building Blocks for Next Chapter
- Learned: Type safety at compile and runtime
- Mastered: Validation and type inference
- Ready for: Request/response transformation

## Weather Buddy App Status
- Version 7.0: Fully typed with TypeScript
- Features: Type indicators, validation errors, type-safe components
- Visual: Shows type source (manual/inferred/OpenAPI)
- Developer: Export types, explore API endpoints
- Next: Interceptors for auth and logging (Chapter 8)

## Best Practices Established
1. Start with strict TypeScript config
2. Validate at system boundaries
3. Use unknown instead of any
4. Prefer type inference over manual
5. Export learned types for team
6. Use branded types for IDs
7. Transform types at the edge

## Common Mistakes to Avoid
- Trusting API types blindly
- Using 'any' to silence errors
- Not handling optional fields
- Skipping runtime validation
- Over-typing internal code
- Fighting type inference

## TypeScript Configuration
```json
{
  "compilerOptions": {
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "noUncheckedIndexedAccess": true
  }
}
```