Finished 03. Django models

django-girls.md

@@ -64,3 +64,118 @@ python manage.py runserver
 
 ## 2. Django models
 
+Target: create objects that store all posts in the blog.
+
+### 2.1 Objects
+
+In OOP, object containing member data and member function. We try to model the blog's objects as well.
+
+Q: 
+* How will we model blog posts?
+* What is a blog post?
+* What properties should it have?
+
+A:
+* Blog posts need
+  * text with content and title
+  * author
+  * date of created/published
+
+Object's data can be shown as below:
+
+```
+Post
+-------
+title
+text
+author
+created_date
+published_date
+```
+
+Blog object's method:
+* `publish`
+
+### 2.2 Django model
+
+A model in Django is a special kind of obj, saved in `database`. Analogy: A model in database is like a spreadsheet with columns (fields) and rows (data).
+
+#### 2.2.1 Creating and app
+
+For organization, we create a separate app inside the web project, which contains logic and model.
+
+```
+$ python manage.py startapp blog
+```
+
+It created a dir called `/blog` that containing scripts:
+
+```
+djangogirls
+├── blog
+│   ├── admin.py
+│   ├── apps.py
+│   ├── __init__.py
+│   ├── migrations
+│   │   └── __init__.py
+│   ├── models.py
+│   ├── tests.py
+│   └── views.py
+|...
+```
+
+After creating app, `mysite/settings.py` should be changed to let Django notice the app.
+
+```python
+INSTALLED_APPS = [
+    'django.contrib.admin',
+    'django.contrib.auth',
+    'django.contrib.contenttypes',
+    'django.contrib.sessions',
+    'django.contrib.messages',
+    'django.contrib.staticfiles',
+    # first party
+    'blog.apps.BlogConfig',
+]
+```
+
+* `blog.apps.BlogConfig` is the class that in `blog/apps.py` script
+
+#### 2.2.2 Creating a blog post model
+
+For each app, there is a `models.py` that contains models (obj), modify it to contain post obj
+
+```python
+from django.db import models
+from django.conf import settings
+from django.utils import timezone
+
+class Post(models.Model):
+    author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
+    title = models.CharField(max_length=200)
+    text = models.TextField()
+    created_date = models.DateTimeField(default=timezone.now)
+    published_date = models.DateTimeField(blank=True, null=True)
+
+    def publish(self):
+        self.published_date = timezone.now()
+        self.save()
+
+    def __str__(self):
+        return self.title
+```
+
+Explaining Post class:
+* `models.Model` the base class the Post class inherit from. It means `Post` is a Django Model, so Django can save it in database
+* Properties are defined as Django's model data type:
+  * `models.CharField`: A Django model class that define text with limited number of char
+  * `models.TextField`: long text w/o limit
+  * Check django models->fields->field-types
+
+#### 2.2.3 Create tables for models in database
+
+After creating new model, we need to add it into database:
+
+1. Let Django know there is change: `python manage.py makemigrations blog`
+   1. So, Django will prepare a migration file
+2. After prepared migration file `blog/migrations/0001_initial.py`, apply it to database: `python manage.py migrate blog`

src/blog/admin.py

@@ -0,0 +1,3 @@
+from django.contrib import admin
+
+# Register your models here.

src/blog/apps.py

@@ -0,0 +1,5 @@
+from django.apps import AppConfig
+
+
+class BlogConfig(AppConfig):
+    name = 'blog'

src/blog/migrations/0001_initial.py

@@ -0,0 +1,29 @@
+# Generated by Django 3.1.2 on 2020-10-19 04:23
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+import django.utils.timezone
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Post',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('title', models.CharField(max_length=200)),
+                ('text', models.TextField()),
+                ('created_date', models.DateTimeField(default=django.utils.timezone.now)),
+                ('published_date', models.DateTimeField(blank=True, null=True)),
+                ('author', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+    ]

src/blog/models.py

@@ -0,0 +1,17 @@
+from django.db import models
+from django.conf import settings
+from django.utils import timezone
+
+class Post(models.Model):
+    author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
+    title = models.CharField(max_length=200)
+    text = models.TextField()
+    created_date = models.DateTimeField(default=timezone.now)
+    published_date = models.DateTimeField(blank=True, null=True)
+
+    def publish(self):
+        self.published_date = timezone.now()
+        self.save()
+
+    def __str__(self):
+        return self.title

src/blog/tests.py

@@ -0,0 +1,3 @@
+from django.test import TestCase
+
+# Create your tests here.

src/blog/views.py

@@ -0,0 +1,3 @@
+from django.shortcuts import render
+
+# Create your views here.

src/mysite/settings.py

@@ -38,6 +38,8 @@ INSTALLED_APPS = [
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.staticfiles',
+    # first party
+    'blog.apps.BlogConfig',
 ]
 
 MIDDLEWARE = [