Views
Take a request, return a response.
Plain views are written as classes, with a straightforward API that keeps simple views simple, but gives you the power of a full class to handle more complex cases.
from plain.views import View
class ExampleView(View):
def get(self):
return "Hello, world!"
HTTP methods -> class methods
The HTTP methd of the request will map to a class method of the same name on the view.
If a request comes in and there isn't a matching method on the view,
Plain will return a 405 Method Not Allowed response.
from plain.views import View
class ExampleView(View):
def get(self):
pass
def post(self):
pass
def put(self):
pass
def patch(self):
pass
def delete(self):
pass
def trace(self):
pass
The base View class defines default options and head behavior,
but you can override these too.
Return types
For simple plain text and JSON responses,
you don't need to instantiate a Response object.
class TextView(View):
def get(self):
return "Hello, world!"
class JsonView(View):
def get(self):
return {"message": "Hello, world!"}
Template views
The most common behavior for a view is to render a template.
from plain.views import TemplateView
class ExampleView(TemplateView):
template_name = "example.html"
def get_template_context(self):
context = super().get_template_context()
context["message"] = "Hello, world!"
return context
The TemplateView is also the base class for most of the other built-in view classes.
Form views
Standard forms can be rendered and processed by a FormView.
from plain.views import FormView
from .forms import ExampleForm
class ExampleView(FormView):
template_name = "example.html"
form_class = ExampleForm
success_url = "." # Redirect to the same page
def form_valid(self, form):
# Do other successfull form processing here
return super().form_valid(form)
Rendering forms is done directly in the HTML.
{% extends "base.html" %}
{% block content %}
<form method="post">
{{ csrf_input }}
<!-- Render general form errors -->
{% for error in form.non_field_errors %}
<div>{{ error }}</div>
{% endfor %}
<!-- Render form fields individually (or with Jinja helps or other concepts) -->
<label for="{{ form.email.html_id }}">Email</label>
<input
type="email"
name="{{ form.email.html_name }}"
id="{{ form.email.html_id }}"
value="{{ form.email.value() or '' }}"
autocomplete="email"
autofocus
required>
{% if form.email.errors %}
<div>{{ form.email.errors|join(', ') }}</div>
{% endif %}
<button type="submit">Save</button>
</form>
{% endblock %}
Object views
The object views support the standard CRUD (create, read/detail, update, delete) operations, plus a list view.
from plain.views import DetailView, CreateView, UpdateView, DeleteView, ListView
class ExampleDetailView(DetailView):
template_name = "detail.html"
def get_object(self):
return MyObjectClass.objects.get(
pk=self.url_kwargs["pk"],
user=self.request.user, # Limit access
)
class ExampleCreateView(CreateView):
template_name = "create.html"
form_class = CustomCreateForm
success_url = "."
class ExampleUpdateView(UpdateView):
template_name = "update.html"
form_class = CustomUpdateForm
success_url = "."
def get_object(self):
return MyObjectClass.objects.get(
pk=self.url_kwargs["pk"],
user=self.request.user, # Limit access
)
class ExampleDeleteView(DeleteView):
template_name = "delete.html"
success_url = "."
# No form class necessary.
# Just POST to this view to delete the object.
def get_object(self):
return MyObjectClass.objects.get(
pk=self.url_kwargs["pk"],
user=self.request.user, # Limit access
)
class ExampleListView(ListView):
template_name = "list.html"
def get_objects(self):
return MyObjectClass.objects.filter(
user=self.request.user, # Limit access
)
Response exceptions
At any point in the request handling,
a view can raise a ResponseException to immediately exit and return the wrapped response.
This isn't always necessary, but can be useful for raising rate limits or authorization errors when you're a couple layers deep in the view handling or helper functions.
from plain.views import DetailView
from plain.views.exceptions import ResponseException
from plain.http import Response
class ExampleView(DetailView):
def get_object(self):
if self.request.user.exceeds_rate_limit:
raise ResponseException(
Response("Rate limit exceeded", status=429)
)
return AnExpensiveObject()
Error views
By default, HTTP errors will be rendered by templates/<status_code>.html or templates/error.html.
You can define your own error views by pointing the HTTP_ERROR_VIEWS setting to a dictionary of status codes and view classes.
# app/settings.py
HTTP_ERROR_VIEWS = {
404: "errors.NotFoundView",
}
# app/errors.py
from plain.views import View
class NotFoundView(View):
def get(self):
# A custom implementation or error view handling
pass
Redirect views
from plain.views import RedirectView
class ExampleRedirectView(RedirectView):
url = "/new-location/"
permanent = True
CSRF exemption
from plain.views import View
from plain.views.csrf import CsrfExemptViewMixin
class ExemptView(CsrfExemptViewMixin, View):
def post(self):
return "Hello, world!"
1from plain.exceptions import ImproperlyConfigured, ObjectDoesNotExist
2from plain.http import Http404, Response, ResponseRedirect
3
4from .forms import FormView
5from .templates import TemplateView
6
7
8class ObjectTemplateViewMixin:
9 context_object_name = ""
10
11 def get(self) -> Response:
12 self.load_object()
13 return self.render_template()
14
15 def load_object(self) -> None:
16 try:
17 self.object = self.get_object()
18 except ObjectDoesNotExist:
19 raise Http404
20
21 if not self.object:
22 # Also raise 404 if the object is None
23 raise Http404
24
25 def get_object(self): # Intentionally untyped... subclasses must override this.
26 raise NotImplementedError(
27 f"get_object() is not implemented on {self.__class__.__name__}"
28 )
29
30 def get_template_context(self) -> dict:
31 """Insert the single object into the context dict."""
32 context = super().get_template_context() # type: ignore
33 context["object"] = self.object
34 if self.context_object_name:
35 context[self.context_object_name] = self.object
36 elif hasattr(self.object, "_meta"):
37 context[self.object._meta.model_name] = self.object
38 return context
39
40 def get_template_names(self) -> list[str]:
41 """
42 Return a list of template names to be used for the request. May not be
43 called if render_to_response() is overridden. Return the following list:
44
45 * the value of ``template_name`` on the view (if provided)
46 object instance that the view is operating upon (if available)
47 * ``<package_label>/<model_name><template_name_suffix>.html``
48 """
49 if self.template_name: # type: ignore
50 return [self.template_name] # type: ignore
51
52 # If template_name isn't specified, it's not a problem --
53 # we just start with an empty list.
54 names = []
55
56 # The least-specific option is the default <app>/<model>_detail.html;
57 # only use this if the object in question is a model.
58 if hasattr(self.object, "_meta"):
59 object_meta = self.object._meta
60 names.append(
61 f"{object_meta.package_label}/{object_meta.model_name}{self.template_name_suffix}.html"
62 )
63
64 return names
65
66
67class DetailView(ObjectTemplateViewMixin, TemplateView):
68 """
69 Render a "detail" view of an object.
70
71 By default this is a model instance looked up from `self.queryset`, but the
72 view will support display of *any* object by overriding `self.get_object()`.
73 """
74
75 template_name_suffix = "_detail"
76
77
78class CreateView(ObjectTemplateViewMixin, FormView):
79 """
80 View for creating a new object, with a response rendered by a template.
81 """
82
83 def post(self) -> Response:
84 """
85 Handle POST requests: instantiate a form instance with the passed
86 POST variables and then check if it's valid.
87 """
88 # Context expects self.object to exist
89 self.load_object()
90 return super().post()
91
92 def load_object(self) -> None:
93 self.object = None
94
95 # TODO? would rather you have to specify this...
96 def get_success_url(self):
97 """Return the URL to redirect to after processing a valid form."""
98 if self.success_url:
99 url = self.success_url.format(**self.object.__dict__)
100 else:
101 try:
102 url = self.object.get_absolute_url()
103 except AttributeError:
104 raise ImproperlyConfigured(
105 "No URL to redirect to. Either provide a url or define"
106 " a get_absolute_url method on the Model."
107 )
108 return url
109
110 def form_valid(self, form):
111 """If the form is valid, save the associated model."""
112 self.object = form.save()
113 return super().form_valid(form)
114
115
116class UpdateView(ObjectTemplateViewMixin, FormView):
117 """View for updating an object, with a response rendered by a template."""
118
119 template_name_suffix = "_form"
120
121 def post(self) -> Response:
122 """
123 Handle POST requests: instantiate a form instance with the passed
124 POST variables and then check if it's valid.
125 """
126 self.load_object()
127 return super().post()
128
129 def get_success_url(self):
130 """Return the URL to redirect to after processing a valid form."""
131 if self.success_url:
132 url = self.success_url.format(**self.object.__dict__)
133 else:
134 try:
135 url = self.object.get_absolute_url()
136 except AttributeError:
137 raise ImproperlyConfigured(
138 "No URL to redirect to. Either provide a url or define"
139 " a get_absolute_url method on the Model."
140 )
141 return url
142
143 def form_valid(self, form):
144 """If the form is valid, save the associated model."""
145 self.object = form.save()
146 return super().form_valid(form)
147
148 def get_form_kwargs(self):
149 """Return the keyword arguments for instantiating the form."""
150 kwargs = super().get_form_kwargs()
151 kwargs.update({"instance": self.object})
152 return kwargs
153
154
155class DeleteView(ObjectTemplateViewMixin, TemplateView):
156 """
157 View for deleting an object retrieved with self.get_object(), with a
158 response rendered by a template.
159 """
160
161 template_name_suffix = "_confirm_delete"
162
163 def get_form_kwargs(self):
164 """Return the keyword arguments for instantiating the form."""
165 kwargs = super().get_form_kwargs()
166 kwargs.update({"instance": self.object})
167 return kwargs
168
169 def get_success_url(self):
170 if self.success_url:
171 return self.success_url.format(**self.object.__dict__)
172 else:
173 raise ImproperlyConfigured("No URL to redirect to. Provide a success_url.")
174
175 def post(self):
176 self.load_object()
177 self.object.delete()
178 return ResponseRedirect(self.get_success_url())
179
180
181class ListView(TemplateView):
182 """
183 Render some list of objects, set by `self.get_queryset()`, with a response
184 rendered by a template.
185 """
186
187 template_name_suffix = "_list"
188 context_object_name = "objects"
189
190 def get(self) -> Response:
191 self.objects = self.get_objects()
192 return super().get()
193
194 def get_objects(self):
195 raise NotImplementedError(
196 f"get_objects() is not implemented on {self.__class__.__name__}"
197 )
198
199 def get_template_context(self) -> dict:
200 """Insert the single object into the context dict."""
201 context = super().get_template_context() # type: ignore
202 context[self.context_object_name] = self.objects
203 return context
204
205 def get_template_names(self) -> list[str]:
206 """
207 Return a list of template names to be used for the request. May not be
208 called if render_to_response() is overridden. Return the following list:
209
210 * the value of ``template_name`` on the view (if provided)
211 object instance that the view is operating upon (if available)
212 * ``<package_label>/<model_name><template_name_suffix>.html``
213 """
214 if self.template_name: # type: ignore
215 return [self.template_name] # type: ignore
216
217 # If template_name isn't specified, it's not a problem --
218 # we just start with an empty list.
219 names = []
220
221 # The least-specific option is the default <app>/<model>_detail.html;
222 # only use this if the object in question is a model.
223 if hasattr(self.objects, "model") and hasattr(self.objects.model, "_meta"):
224 object_meta = self.objects.model._meta
225 names.append(
226 f"{object_meta.package_label}/{object_meta.model_name}{self.template_name_suffix}.html"
227 )
228
229 return names