lcbp3/specs/05-Engineering-Guidelines/05-06-code-snippets.md

Code Snippets

Version: 1.8.4
Last Updated: 2026-03-24
Location: specs/05-Engineering-Guidelines/05-06-code-snippets.md

---

Backend DTO Pattern

// [dto-new] → Create DTO with validator
@IsUUID()
@ApiProperty({ description: 'Project UUID (public)' })
projectUuid!: string;

@IsOptional()
@IsInt()
@ApiProperty({ required: false, description: 'Internal project ID' })
projectId?: number; // resolved internally, never from client

---

Frontend Form Pattern

// [form-rhf-zod] → Create form schema + hook
const schema = z.object({
  projectUuid: z.string().uuid('รหัสโครงการไม่ถูกต้อง'),
  title: z.string().min(3, 'กรุณากรอกหัวข้ออย่างน้อย 3 ตัวอักษร'),
});
const form = useForm({ resolver: zodResolver(schema) });

---

UUID Safe Pattern

// [uuid-safe] → Check UUID before use
const safeUuid = (val: string | number): string => {
  if (typeof val === 'number') {
    Logger.warn(`UUID received as number: ${val}`);
    return String(val); // or throw error per policy
  }
  return val;
};

---

Backend Error Handling Pattern

// [backend-error] → Standard error handling
if (!entity) {
  this.logger.warn(`Entity not found: ${uuid}`, 'Service.findOne');
  throw new NotFoundException(`Resource with UUID ${uuid} not found`);
}

---

Frontend Query Pattern

// [frontend-query] → TanStack Query v5 standard
const { data, error, isLoading } = useQuery({
  queryKey: ['correspondence', uuid],
  queryFn: () => api.get(`/correspondences/${uuid}`),
});
// v5: onError removed from useQuery — handle error via return value
if (error) toast.error('ไม่สามารถโหลดข้อมูลได้');

---

Redis Cache Pattern

// [redis-cache] → Cache-Aside Pattern
const cacheKey = `correspondence:${uuid}`;
const cached = await this.cacheManager.get(cacheKey);
if (cached) return cached;
const entity = await this.repo.findOneBy({ uuid });
if (entity) {
  await this.cacheManager.set(cacheKey, entity, 300); // 5 minutes
}
return entity;

---

Reference

• Backend Guidelines
• Frontend Guidelines
• Testing Strategy