docs: Add 03-views.md

Author: devpla

docs/03-views.md

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+# 03. Views
+
+## Views
+뷰는 Django 어플리케이션이 특정 기능과 템플릿을 제공하는 웹페이지의 종류
+
+### `polls/views.py`
+```python
+from django.shortcuts import render, get_object_or_404
+from django.http import HttpResponse, Http404
+from django.template import loader
+from .models import Question
+
+
+def index(request):
+    latest_question_list = Question.objects.order_by('-pub_date')[:5]
+    context = {'latest_question_list': latest_question_list}
+    return render(request, 'polls/index.html', context)
+
+
+def detail(request, question_id):
+    # 객체가 존재하지 않으면 Http404 에러 발생하는 메서드
+    question = get_object_or_404(Question, pk=question_id)
+    return render(request, 'polls/detail.html', {'question': question})
+
+
+def results(request, question_id):
+    response = f"You're looking at the results of question {question_id}"
+    return HttpResponse(response)
+
+
+def vote(request, question_id):
+    return HttpResponse(f"You're voting on question {question_id}")
+```
+
+### `polls/urls.py`
+```python
+from django.urls import path
+from . import views
+
+app_name = 'polls'  # URL의 이름공간
+urlpatterns = [
+    # ex: /polls/
+    path('', views.index, name='index'),
+
+    # ex: /polls/5/
+    path('<int:question_id>/', views.detail, name='detail'),
+
+    # ex: /polls/5/results/
+    path('<int:question_id>/results/', views.results, name='results'),
+
+    # ex: /polls/5/vote/
+    path('<int:question_id>/vote/', views.vote, name='vote'),
+]
+```
+
+### `polls/templates/polls/index.html`
+```html
+{% if latest_question_list %}
+  <ul>
+    {% for question in latest_question_list %}
+      <li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>
+    {% endfor %}
+  </ul>
+{% else %}
+  <p>No polls are available.</p>
+{% endif %}
+```
+
+### `polls/templates/polls/detail.html`
+```html
+<h1>{{ question.question_text }}</h1>
+<ul>
+{% for choice in question.choice_set.all %}
+    <li>{{ choice.choice_text }}</li>
+{% endfor %}
+</ul>
+```