690327:1611 Fixing Refactor ADR-019 Naming convention uuid #187

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

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+# Code Snippets
+
+**Version:** 1.8.4  
+**Last Updated:** 2026-03-24  
+**Location:** `specs/05-Engineering-Guidelines/05-06-code-snippets.md`
+
+---
+
+## Backend DTO Pattern
+
+```typescript
+// [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
+
+```typescript
+// [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
+
+```typescript
+// [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
+
+```typescript
+// [backend-error] → Standard error handling
+if (!entity) {
+  this.logger.warn(`Entity not found: ${uuid}`, 'Service.findOne');
+  throw new NotFoundException(`Resource with UUID ${uuid} not found`);
+}
+```
+
+---
+
+## Frontend Query Pattern
+
+```typescript
+// [frontend-query] → TanStack Query v5 standard
+const { data, error, isLoading } = useQuery({
+  queryKey: ['correspondence', uuid],
+  queryFn: () => api.get(`/correspondences/${uuid}`),
+});
+// v5: onError removed from useQuery — handle error via return value
+if (error) toast.error('ไม่สามารถโหลดข้อมูลได้');
+```
+
+---
+
+## Redis Cache Pattern
+
+```typescript
+// [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](05-02-backend-guidelines.md)
+- [Frontend Guidelines](05-03-frontend-guidelines.md)
+- [Testing Strategy](05-04-testing-strategy.md)