create model

Date: March 17th 2016
Last updated: March 17th 2016

A model is created in models.py and states exactly how the database should be designed. In this example I am going to add a full suite of tables which contain different field types and input restrictions. Useful tutorials worth looking at:

• https://docs.djangoproject.com/en/1.9/intro/tutorial02/
• https://docs.djangoproject.com/en/1.9/ref/models/fields/
• https://docs.djangoproject.com/en/1.9/topics/db/examples/many_to_many/
• http://stackoverflow.com/questions/849142/how-to-limit-the-maximum-value-of-a-numeric-field-in-a-django-model

The steps:

# add to models.py
code below

# update settings.py (inside mysite directory, not the app)
#< snipped >
INSTALLED_APPS = [
    'surferprofile.apps.SurferprofileConfig', #<==== added app
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
]
#< snipped >

# makemigrations
python3 manage.py makemigrations surferprofile

# migrate
python3 manage.py migrate

# output from migrate command
#Operations to perform:
#  Apply all migrations: admin, auth, contenttypes, sessions, surferprofile
#Running migrations:
#  Rendering model states... DONE
#  Applying surferprofile.0001_initial... OK

models.py
Things to note include ForeignKey and ManyToMany relationships,

from django.db import models

class Beach(models.Model):
    beachname = models.CharField(max_length=20)
    beachcity = models.CharField(max_length=20)
    beachsuburb = models.CharField(max_length=20)
    beachcountry = models.CharField(max_length=20)
    beachpostcode = models.IntegerField()

class Wave(models.Model):
    # break choice
    POINTBREAK = 'PB'
    BEACHBREAK = 'BB'
    REEF = 'RF'
    WAVES_CHOICE = ((POINTBREAK, 'Point break'), \
                    (BEACHBREAK, 'Beach break'), \
                    (REEF, 'Reef'),)
    wavebreak = models.CharField(max_length=2, choices=WAVES_CHOICE,
                                 default=BEACHBREAK)
    # Wave type
    CLOSEOUTS = 'CO'
    CRUMBLY = 'CR'
    REFORMS = 'RE'
    TUBING = 'TU'
    DOUBLEUPS = 'DU'
    WAVE_TYPE = ((CLOSEOUTS, 'Closeouts'),
                (CRUMBLY, 'Crumbly'),
                (REFORMS, 'Reforming'),
                (TUBING, 'Hollow tubing'),
                (DOUBLEUPS, 'Double-ups'),)
    wavetype = models.CharField(max_length=2, choices=WAVE_TYPE,
                                 default=TUBING)
    beach_id = models.ForeignKey(Beach, on_delete=models.CASCADE)

class Board(models.Model):
    boardlength = models.DecimalField(max_digits=4,decimal_places=2)
    boardwidth = models.DecimalField(max_digits=4,decimal_places=2)
    boardthickness = models.DecimalField(max_digits=4,decimal_places=2)
    boardvolume = models.DecimalField(max_digits=4,decimal_places=2)
    boardmake = models.CharField(max_length=20)
    boardshaper = models.CharField(max_length=40)

class Fin(models.Model):
    finsystem = models.CharField(max_length=20)
    fintemplate = models.CharField(max_length=20)
    finname = models.CharField(max_length=20)

class Trick(models.Model):
    trickname = models.CharField(max_length=20)

class Surfer(models.Model):
    profilefirstname = models.CharField(max_length=20)
    profilelastname = models.CharField(max_length=20)
    profileheight = models.DecimalField(max_digits=4, decimal_places=1)
    profileweight = models.DecimalField(max_digits=4, decimal_places=1)
    profilehomebeach = models.ForeignKey(Beach, on_delete=models.CASCADE)
    profilefavwave = models.ForeignKey(Wave, on_delete=models.CASCADE)
    profilefins = models.ManyToManyField(Fin)
    profiletricks = models.ManyToManyField(Trick)
    profileboards = models.ManyToManyField(Board)

class SurfDiary(models.Model):
    surfdiary_wavesize = models.IntegerField()
    surfdiary_starttime = models.DateTimeField('start time')
    surfdiary_endtime = models.DateTimeField('end time')

    SCORE_CHOICES = zip( range(1,11), range(1,11) )
    surfdiary_wavequality = models.IntegerField(choices=SCORE_CHOICES, blank=True)
    surfdiary_selfscore = models.IntegerField(choices=SCORE_CHOICES, blank=True)
    surfdiary_crowdscore = models.IntegerField(choices=SCORE_CHOICES, blank=True)

    NONE = 'NO'
    ONSHORE = 'ON'
    OFFSHORE = 'OF'
    CROSSSHORE = 'CR'
    WINDDIR = ((NONE, 'No wind'),
                (ONSHORE, 'On shore'),
                (OFFSHORE, 'Off shore'),
                (CROSSSHORE, 'Cross shore'),)
    surfdiary_winddir = models.CharField(max_length=2, choices=WINDDIR)
    surfdiary_notes = models.CharField(max_length=200)

    surfdiary_profile = models.ForeignKey(Surfer, on_delete=models.CASCADE)
    surfdiary_board = models.ForeignKey(Board, on_delete=models.CASCADE)
    surfdiary_fin = models.ForeignKey(Fin, on_delete=models.CASCADE)
    surfdiary_beach  = models.ForeignKey(Beach, on_delete=models.CASCADE)
    surfdiary_wave  = models.ForeignKey(Wave, on_delete=models.CASCADE)
    surfdiary_favtrick  = models.ForeignKey(Trick, on_delete=models.CASCADE)

Schema
Note the separation of the default tables and the models just created. This is useful to visualise how each class gets mapped to a table in the database schema. Also note that all columns have been given NOT NULL by default, I will need to change this in the future.