Building RESTful APIs with NestJS: Complete Tutorial

# Building RESTful APIs with NestJS

REST (Representational State Transfer) is an architectural style for designing networked applications. NestJS makes building RESTful APIs straightforward with its decorator-based approach.

## REST Principles

### 1. Stateless Each request must contain all information needed to process it.

### 2. Resource-based URLs Use nouns to represent resources: `/users`, `/posts`, `/categories`

### 3. HTTP Methods - GET: Retrieve resources - POST: Create new resources - PUT/PATCH: Update resources - DELETE: Remove resources

## NestJS Implementation

### Controller Example ```typescript @Controller('posts') export class PostController { constructor(private readonly postService: PostService) {}

@Get() findAll(@Query() query: PostQueryDto) { return this.postService.findAll(query); }

@Post() @UseGuards(AuthGuard('jwt')) create(@Body() createPostDto: CreatePostDto, @CurrentUser() user) { return this.postService.create(createPostDto, user.id); }

@Get(':id') findOne(@Param('id') id: string) { return this.postService.findById(id); }

@Patch(':id') @UseGuards(AuthGuard('jwt')) update(@Param('id') id: string, @Body() updatePostDto: UpdatePostDto) { return this.postService.update(id, updatePostDto); }

@Delete(':id') @UseGuards(AuthGuard('jwt')) remove(@Param('id') id: string) { return this.postService.remove(id); } } ```

## Best Practices

1. **Consistent naming**: Use plural nouns for collections 2. **Proper status codes**: Return appropriate HTTP status codes 3. **Error handling**: Implement global exception filters 4. **Validation**: Use DTOs with class-validator 5. **Documentation**: Add Swagger decorators

Building well-designed APIs is crucial for maintainable applications.