# Tutorial 2: Requests and Responses From this point we're going to really start covering the core of REST framework. Let's introduce a couple of essential building blocks. ## Request objects REST framework intoduces a `Request` object that extends the regular `HttpRequest`, and provides more flexible request parsing. The core functionality of the `Request` object is the `request.DATA` attribute, which is similar to `request.POST`, but more useful for working with Web APIs. request.POST # Only handles form data. Only works for 'POST' method. request.DATA # Handles arbitrary data. Works any HTTP request with content. ## Response objects REST framework also introduces a `Response` object, which is a type of `TemplateResponse` that takes unrendered content and uses content negotiation to determine the correct content type to return to the client. return Response(data) # Renders to content type as requested by the client. ## Status codes Using numeric HTTP status codes in your views doesn't always make for obvious reading, and it's easy to not notice if you get an error code wrong. REST framework provides more explicit identifiers for each status code, such as `HTTP_400_BAD_REQUEST` in the `status` module. It's a good idea to use these throughout rather than using numeric identifiers. ## Wrapping API views REST framework provides two wrappers you can use to write API views. 1. The `@api_view` decorator for working with function based views. 2. The `APIView` class for working with class based views. These wrappers provide a few bits of functionality such as making sure you recieve `Request` instances in your view, and adding context to `Response` objects so that content negotiation can be performed. The wrappers also provide behaviour such as returning `405 Method Not Allowed` responses when appropriate, and handling any `ParseError` exception that occurs when accessing `request.DATA` with malformed input. ## Pulling it all together Okay, let's go ahead and start using these new components to write a few views. We don't need our `JSONResponse` class anymore, so go ahead and delete that. Once that's done we can start refactoring our views slightly. from blog.models import Comment from blog.serializers import CommentSerializer from rest_framework import status from rest_framework.decorators import api_view from rest_framework.response import Response @api_view(['GET', 'POST']) def comment_root(request): """ List all comments, or create a new comment. """ if request.method == 'GET': comments = Comment.objects.all() serializer = CommentSerializer(instance=comments) return Response(serializer.data) elif request.method == 'POST': serializer = CommentSerializer(request.DATA) if serializer.is_valid(): comment = serializer.object comment.save() return Response(serializer.data, status=status.HTTP_201_CREATED) else: return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST) Our instance view is an improvement over the previous example. It's a little more concise, and the code now feels very similar to if we were working with the Forms API. We're also using named status codes, which makes the response meanings more obvious. @api_view(['GET', 'PUT', 'DELETE']) def comment_instance(request, pk): """ Retrieve, update or delete a comment instance. """ try: comment = Comment.objects.get(pk=pk) except Comment.DoesNotExist: return Response(status=status.HTTP_404_NOT_FOUND) if request.method == 'GET': serializer = CommentSerializer(instance=comment) return Response(serializer.data) elif request.method == 'PUT': serializer = CommentSerializer(request.DATA, instance=comment) if serializer.is_valid(): comment = serializer.object comment.save() return Response(serializer.data) else: return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST) elif request.method == 'DELETE': comment.delete() return Response(status=status.HTTP_204_NO_CONTENT) This should all feel very familiar - there's not a lot different to working with regular Django views. Notice that we're no longer explicitly tying our requests or responses to a given content type. `request.DATA` can handle incoming `json` requests, but it can also handle `yaml` and other formats. Similarly we're returning response objects with data, but allowing REST framework to render the response into the correct content type for us. ## Adding optional format suffixes to our URLs To take advantage of the fact that our responses are no longer hardwired to a single content type let's add support for format suffixes to our API endpoints. Using format suffixes gives us URLs that explicitly refer to a given format, and means our API will be able to handle URLs such as [http://example.com/api/items/4.json][json-url]. Start by adding a `format` keyword argument to both of the views, like so. def comment_root(request, format=None): and def comment_instance(request, pk, format=None): Now update the `urls.py` file slightly, to append a set of `format_suffix_patterns` in addition to the existing URLs. from django.conf.urls import patterns, url from rest_framework.urlpatterns import format_suffix_patterns urlpatterns = patterns('blogpost.views', url(r'^$', 'comment_root'), url(r'^(?P[0-9]+)$', 'comment_instance') ) urlpatterns = format_suffix_patterns(urlpatterns) We don't necessarily need to add these extra url patterns in, but it gives us a simple, clean way of refering to a specific format. ## How's it looking? Go ahead and test the API from the command line, as we did in [tutorial part 1][tut-1]. Everything is working pretty similarly, although we've got some nicer error handling if we send invalid requests. **TODO: Describe using accept headers, content-type headers, and format suffixed URLs** Now go and open the API in a web browser, by visiting [http://127.0.0.1:8000/][devserver]." **Note: Right now the Browseable API only works with the CBV's. Need to fix that.** ### Browsability Because the API chooses a return format based on what the client asks for, it will, by default, return an HTML-formatted representation of the resource when that resource is requested by a browser. This allows for the API to be easily browsable and usable by humans. See the [browsable api][browseable-api] topic for more information about the browsable API feature and how to customize it. ## What's next? In [tutorial part 3][tut-3], we'll start using class based views, and see how generic views reduce the amount of code we need to write. [json-url]: http://example.com/api/items/4.json [devserver]: http://127.0.0.1:8000/ [browseable-api]: ../topics/browsable-api.md [tut-1]: 1-serialization.md [tut-3]: 3-class-based-views.md a> 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720