Sorry. I should have typed the ID as lower case id in
{% if user.Family. <http://user.family.id/>id =
object.Teacher.id.Family.<http://object.teacher.id.family.id/>
id %}
On Wednesday, July 24, 2013 3:28:52 PM UTC-4, Chris Ryan wrote:
>
> Thank you so much for the reply and help. I am not stuck with this
> database format and can change it as necessary. I will modify it as you
> suggested (let Django create the primary key, remove the ID suffix from the
> column names, etc.). I will then look for the managers as you suggested.
>
> I did find a solution to what I was trying doing. I was reading through
> the Python documentation and then through the Django documentation (for the
> up-teenth time) and discovered that I can "move backward" through the
> relationship chain easily (I'm still not sure what the proper phrase is for
> what I'm trying to do). For example, I can display the Family.Name by
> simply doing something like this:
>
> {{ object.TeacherID.ID.FamilyID }}
>
> So, now I can do something like this:
>
> {% if user.FamilyID = object.TeacherID.ID.FamilyID %}
>
>
> Or, after making the changes that you suggested I can do this (and use the
> actual ID numbers for comparison)
>
> {% if user.Family.ID = object.Teacher.ID.Family.ID %}
>
> Thank you again for the information that you provided. It will greatly
> help me move forward from here.
>
> -Chris
>
>
>
> On Wednesday, July 24, 2013 2:51:43 PM UTC-4, ke1g wrote:
>>
>> First, is this a pre-existing data base whose format you are stuck with?
>>
>> While your models probably can be made to work, it is more common to let
>> Django take care of creating a single primary key in a model (called "id"
>> (lower case) by default).
>>
>> Also, while ForeignKey fields are implemented by storing the primary key
>> value of the desired row in the other table, that, too, is intended to be
>> hidden, so when you make a reference through a ForeignKey field, the ORM
>> actually hands you an instance of the foreign Model, not the id. That is:
>>
>> instanceOfCourseCatalog.TeacherID
>>
>> is an instance of Teacher, not the TeacherID of a teacher. To get the id
>> integer, for those very rare cases in which it is valuable, you woudl use:
>>
>> instanceOfCourseCatalog.TeacherID.TeacherID
>>
>> If you go the normal way and let Django create the primary key fields by
>> the default name "id", and if, to better describe what is happening,
>> removed the "ID from the end of your ForeignKey field names and, also a
>> convention, made them lowercase, the lines above lines would become,
>> respectively:
>>
>> instanceOfCourseCatalog.teacher
>>
>> and
>>
>> instanceOfCourseCatalog.teacher.id
>>
>> In this case Django would have added a "manager" to the Teacher model
>> called "coursecatalog_set" (or just possibly "course_catalog_set", not
>> certain and don't have time to search the documents now), but whose name
>> your can specify with the "related_name" argument to the ForeignKey field.
>> This manager has all the usual queryset methods, so you can append ".all()'
>> to get an array of all the CourseCatalog objects with that Teacher. See
>> https://docs.djangoproject.com/en/1.5/topics/db/queries/#backwards-related-objects
>>
>> Bill
>>
>>
>> On Wed, Jul 24, 2013 at 8:37 AM, Chris Ryan <[email protected]>wrote:
>>
>>> I have spent hours trying to find the answer to this. What makes it even
>>> more frustrating is that I'm new to django development and not a real
>>> programmer by trade (I am a UNIX admin) so I am struggling to label what I
>>> am trying to do so that I can search for an answer.
>>>
>>>
>>> Here's what I have:
>>>
>>>
>>> In my models.py file I have the following class definitions:
>>>
>>>
>>> class Family(models.Model):
>>>
>>> ...
>>>
>>> FamilyID = models.AutoField(primary_key=True)
>>>
>>> Name = models.CharField(verbose_name="Family Name")
>>>
>>>
>>>
>>> ------------------------------------------------------------------------------------------------
>>>
>>>
>>> class FamilyMember(AbstractUser):
>>>
>>> ....
>>>
>>> ID = models.AutoField(primary_key=True)
>>>
>>> FamilyID = models.ForeignKey(Family, blank=True, null=True)
>>>
>>> ...
>>>
>>>
>>> ------------------------------------------------------------------------------------------------
>>>
>>>
>>> class Teacher(models.Model):
>>>
>>> ...
>>>
>>> TeacherID = models.AutoField(primary_key=True)
>>>
>>> ID = models.OneToOneField(FamilyMember)
>>>
>>> ...
>>>
>>>
>>> ------------------------------------------------------------------------------------------------
>>>
>>>
>>>
>>> class CourseCatalog(models.Model):
>>>
>>> ...
>>>
>>> TeacherID = models.ForeignKey(Teacher, blank=True, null=True)
>>>
>>> ...
>>>
>>>
>>> ------------------------------------------------------------------------------------------------
>>>
>>>
>>>
>>>
>>> So, there is a table called Family that I belong to. It holds my family
>>> name and a couple of other fields.
>>>
>>> There is then a one-to-many relationship from that to the FamilyMember
>>> table. In this table I have a record for each member of my family.
>>>
>>> The FamilyMember table is also being used as the authentication table
>>> for my site. I have not replaced the default security model but only
>>> abstracted it and added additional fields.
>>>
>>> I am a teacher so there is also a record in the Teacher table. This
>>> table contains the FamilyMember.ID field.
>>>
>>> That's the setup for me. My main information is in the FamilyMember
>>> table and my FamilyMember.ID field is stored in the Family and the Teacher
>>> tables.
>>>
>>>
>>> On to the list of classes...
>>>
>>>
>>> There is a table called CourseCatalog that contains information about a
>>> class that I will teach. One of the columns is called TeacherID and this
>>> stores the TeacherID from the Teacher table. I set it up this way so that
>>> an admin can add a class and then assign it only to a teacher. The drop
>>> down list should not include FamilyMembers that are not teachers.
>>>
>>>
>>> Here are my questions and problems:
>>>
>>>
>>> - I want to log into the website as myself and modify only my classes.
>>> It would also be OK to modify the classes of everyone in my family. Either
>>> solution would be fine. However, I can't figure out how to do either of
>>> these things.
>>>
>>> - It seems to me that what I'm doing is trying to go backwards in the
>>> relationship chain. I have my CourseCatalog record that includes the
>>> TeacherID. I need to look that ID up in the Teacher table to get the
>>> FamilyMember.ID. I then need to use that to look up the record in the
>>> FamilyMember table. Once I have that, I can get the username and compare it
>>> to the username of the logged in user (me). Finally, I can filter on
>>> records where these two match.
>>>
>>> - I'm wondering if I have architected my database wrong. Is there an
>>> easier way to do this? Maybe I should get rid of the Teacher table and just
>>> use a boolean for teacher in the FamilyMember table. The concern that I
>>> have with this is when I start working on the Student table. I need to
>>> store more information about a student (allergy, emergency contacts, etc)
>>> and don't think it is appropriate to add those fields to the FamilyMember
>>> table because they are only used for students.
>>>
>>> - I'm asking for you experts to help guide me through this. Any advice
>>> is greatly appreciated.
>>>
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>>>
>>>
>>
>>
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