Re: ManyToManyField is this right?

Looking at that I think I may need to add a foreignkey to cert_types relating to person since a person can have multiple certification types (NRA Instructor, CCL Instructor, etc).

On Wed, Jun 27, 2012 at 11:40 AM, David Wagner <cptnwinky@gmail.com> wrote:

i think I may just be over thinking this. The last time I did any significant coding for the web as pre-php5 and so this whole MVC thing is something to adapt too for sure.

I think I need to start thinking of the Model in the same way I would design a database back in the day with phpMyAdmin. I think I'm getting bogged down in trying to understand how it will relate to the View. Perhaps I need to just put the View out of my mind for the time being.

So thinking of this as just a database schema it would be something like (in psuedo-code)....

cert_types

• type
• date_created

certs

• type = foreignkey(cert_types)
• name
• state (optional)
• date_created

person

• name
• etc...
• certificates = foreignkey(certs)

Does that make sense? If so each table would be represented by a single class and I think I understand then how they relate to each other and I just need to stop worrying about the View.

Thanks for all your patience everyone as well. Like I said, I'm not classically trained in computer science so there are a lot of concepts that elude me and some lingo that I don't get but the concepts I may grasp if I just understand the translation.

On Wed, Jun 27, 2012 at 10:55 AM, Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:

On Wed, 27 Jun 2012 08:02:37 -0700, David Wagner <cptnwinky@gmail.com>
declaimed the following in gmane.comp.python.django.user:

>
> class NRA_Certs(models.Model):
>     CRSO = models.BooleanField(blank=True, null=True, "Chief Range Safety
> Officer")
>     HFS = models.BooleanField(blank=True, null=True, "Home Firearm Safety")
>     MCR = models.BooleanField(blank=True, null=True, "Metallic Cartridge
> Reloading")
>     PPH = models.BooleanField(blank=True, null=True, "Personal Protection
> in the Home")
>     PPO = models.BooleanField(blank=True, null=True, "Personal Protection
> Outside the Home")
>     PS = models.BooleanField(blank=True, null=True, "Pistol Shooting")
>     RS = models.BooleanField(blank=True, null=True, "Rifle Shooting")
>     SSR = models.BooleanField(blank=True, null=True, "Shotgun Shell
> Reloading")
>     SS = models.BooleanField(blank=True, null=True, "Shotgun Shooting")
>     RTBVDW = models.BooleanField(blank=True, null=True, "Refuse to be a
> Victim Workshop")
>     RTBVO = models.BooleanField(blank=True, null=True, "Refuse to be a
> Victim Online")
>     NMLRA_MP = models.BooleanField(blank=True, null=True, "NMLRA
> Muzzleloading Pistol Shooting")
>     NMLRA_MR = models.BooleanField(blank=True, null=True, "NMLRA
> Muzzleloading Rifle Shooting")
>     NMLRA_MS = models.BooleanField(blank=True, null=True, "NMLRA
> Muzzleloading Shotgun Shooting")
>

       Ugh!...

       I'm not familiar enough with Django's internal format so I'm using a
form of old relational theory notation: tablename(_key_, /foreignkey/,
other, fields...)

NRACertificate(_ID_, certificateName, other, type, specific,
attributes))

       {I forget your individual model so a generic}

Person(_ID_, name, other, stuff)

Person_NRACertificate(_ID_, /personID/, /nracertificateID/,
dateCertified, dateExpires, other, certificate, specfic, data)

       Django can build this intersection table automatically -- but it
would only have _ID_, /personID/, /nracertificateID/! I think, for your
information, you'd want to define your own "through" table to hold the
data specific to an instance of a certificate as held by a person.

       Same with concealed carry permits IF you need a list on a, say, per
state basis.

       Note though, that if the /lists/ don't carry any significant
information beyond the name of the item, you just need one-to-many
configurations. For example, if the only information you track for CCW
is: who (foreign key to Person), license number, issuing state (or other
government entity), date issued, date expires... then a one-to-many is
all you need. (Though you may find you need another one-to-many --
California's rare CCW includes a list of /which/ firearm(s) are
permitted [if you sell one gun and buy a different one, you have to beg
the government to update the CCW with the new gun's information]).

       The NRACertificates table may also not be needed if all it provides
is a list of names to populate a dropdown selection box -- might speed
up processing by just hard-coding the list and saving the name directly
(replace the /nracerticateID/ in the intersect table with the actual
text of the certificate as selected from the dropdown selection.

       Bigger note: You will NOT be using a multiple selection list... More
reasonable is an "add new certificate" button which brings up a form
from which to select one certificate (by name in dropdown), and fields
for the dates, and whatever else is common to certificates.

       When displaying a person, the certificates would be (if I recall
Django terms) a "formset" (where the "form" is for a single
certificate's data).
--
       Wulfraed                 Dennis Lee Bieber         AF6VN
       wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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