DRF類檢視讓你的程式碼DRY起來
阿新 • • 發佈：2020-12-19
剛開始寫`views.py`模組的程式碼，一般都是用`def`定義的函式檢視，不過DRF更推薦使用`class`定義的類檢視，這能讓我們的程式碼更符合DRY（Don't Repeat Yourself）設計原則：
/', views.SnippetDetail.as_view()),
]
urlpatterns = format_suffix_patterns(urlpatterns)
```
**為什麼要加個`as_view()`方法？**
因為`path()`的引數必須是可呼叫的，在原始碼中能看到`elif callable(view)`：
```python
def _path(route, view, kwargs=None, name=None, Pattern=None):
if isinstance(view, (list, tuple)):
# For include(...) processing.
pattern = Pattern(route, is_endpoint=False)
urlconf_module, app_name, namespace = view
return URLResolver(
pattern,
urlconf_module,
kwargs,
app_name=app_name,
namespace=namespace,
)
# callable判斷
elif callable(view):
pattern = Pattern(route, name=name, is_endpoint=True)
return URLPattern(pattern, view, kwargs, name)
else:
raise TypeError('view must be a callable or a list/tuple in the case of include().')
```
`as_view()`方法返回了一個內部定義的可呼叫函式：
```python
@classonlymethod
def as_view(cls, **initkwargs):
"""Main entry point for a request-response process."""
for key in initkwargs:
if key in cls.http_method_names:
raise TypeError(
'The method name %s is not accepted as a keyword argument '
'to %s().' % (key, cls.__name__)
)
if not hasattr(cls, key):
raise TypeError("%s() received an invalid keyword %r. as_view "
"only accepts arguments that are already "
"attributes of the class." % (cls.__name__, key))
# 內部定義了可呼叫函式
def view(request, *args, **kwargs):
self = cls(**initkwargs)
self.setup(request, *args, **kwargs)
if not hasattr(self, 'request'):
raise AttributeError(
"%s instance has no 'request' attribute. Did you override "
"setup() and forget to call super()?" % cls.__name__
)
return self.dispatch(request, *args, **kwargs)
view.view_class = cls
view.view_initkwargs = initkwargs
# take name and docstring from class
update_wrapper(view, cls, updated=())
# and possible attributes set by decorators
# like csrf_exempt from dispatch
update_wrapper(view, cls.dispatch, assigned=())
return view
```
# 使用mixins
DRF提供了`rest_framework.mixins`模組，封裝了類檢視常用的增刪改查方法：
