RE: How to get Foreign Key Objects programmatically?

You may want to look at the model _meta API.

https://docs.djangoproject.com/en/2.0/ref/models/meta/

 

You are looking for a list of all the ForeignKeys, but you also probably want other relations such as OneToOne and ManyToMany.

You probably want something like the get_all_related_objects method:

https://docs.djangoproject.com/en/2.0/ref/models/meta/#migrating-from-the-old-api

 

The fields have an attribute called is_relation, one_to_one, and many_to_one.

 

 

From: django-users@googlegroups.com [mailto:django-users@googlegroups.com] On Behalf Of Rob Schneider
Sent: Tuesday, February 27, 2018 10:46 PM
To: django-users@googlegroups.com
Subject: Re: How to get Foreign Key Objects programmatically?

 

Still a mystery to me.

 

--rms

 

On 28 Feb 2018, at 03:22, Malik Rumi <malik.a.rumi@gmail.com> wrote:

Did you ever find an answer? If so, do you mind sharing it? Thanks.

On Sunday, October 29, 2017 at 9:33:10 AM UTC-7, rmschne wrote:

I'm using Django as front end to a MySQL database. User interface is a terminal program, not a web site.

 

I've written a very simple generic function to edit the fields of one record of a Django "object".  It works fine for editing editable fields. User specifies which field, then is shown the current value, raw_input() for the new value, then save() the record.

 

For fields that connect to Foreign Keys, what I want to do is present to user a simple list of Foreign Key records, from which the user will pick the relevant ID.  I know, given a list and the ID, how to then edit the record by doing a Django get(id=ID) on the Foreign Key table.  What I'm having trouble doing is figuring how

 

1. Identify into a variable the name of the Foreign Key table/object

2. Then with that variable do a call to the relevant Foreign Key table, e.g. ForeignKeyTable.objects.all()

 

See code below for <===WHAT I DO NOT KNOW HOW TO DO IN CODE Below.  I think I need some Django function that gives me the foreign key table in some useable generic form.

 

Hope all this makes sense. 

 

--rms

 

def EditDjangoObjectData(djangoobject,show=False,editonerecord=False):

    """

    EditDjangoObjectData()

        djangoojbect=a django object, e.g. a record in a table

    """

    print "\n****ToDo Note: This routine not yet working on fields with foreign keys!"

    changelist=[]

    ok=True

    while ok:

        change=None

        fields = [(f.name, f.editable) for f in djangoobject._meta.get_fields()]

        if show:

            print "\nfields:\n",fields

            print "django object:\n",djangoobject

        s="\nEditable Fields ('enter' to return): \n"

        fieldlist=[]

        for i in fields:

            if i[1]:   # only for 'editable' fields

                if i[0].lower() <> "id":

                    s=s+i[0]+", "

                    fieldlist.append(i[0])

        s=s+"DELETE or '?'"

        fieldok=False

        while not fieldok:

            fieldtochange=raw_input("Enter field name to change:\n"+s+": ")

            if not fieldtochange:

                return None

            elif fieldtochange.upper()=="DELETE":

                ans=raw_input("...Confirm DELETE by typing 'DELETE': ")

                try:

                    if ans=="DELETE":

                        rtn=djangoobject.delete()

                        print "Deleted. ",rtn

                        return rtn

                except:

                    print "***DELETE Failed.",sys.exc_info()[0]

                    ans=raw_input("Press 'Enter' to continue ... ")

            elif fieldtochange=="?":

                PrintObjectDetails(djangoobject)

            elif fieldtochange in fieldlist:

                fieldok=True

            else:

                print "\n****Error. ",fieldtochange,"is not in list. Try again."

        print "Current Value of Field to Change:",fieldtochange,"is:",getattr(djangoobject, fieldtochange)

**

** In here add some code to show a list of the foreign key records for user to select, e.g. ID, Description, 

**for r in ForeignKey.objects.all():   <== WHAT I DO NOT KNOW HOW TO DO IN CODE.

**    print i.id, i.description

**ID=raw_input("Enter ID:)

**foreignkeyobject=ForeignKey.objects.get(id=ID)    <== WHAT I DO NOT KNOW HOW TO DO IN CODE.

** ... then put that object into the relevant field 

        newvalue=raw_input("Enter New Value: ")

        change="changed ["+fieldtochange+"]"

        print "\nTo Save   :",djangoobject

        print "The Change:",change,"to",newvalue

        if not newvalue:

            return None

        elif newvalue.lower()=="none":

            newvalue=None

        elif newvalue.lower()=="true":

            newvalue==True

        elif newvalue.lower()=="false":

            newvalue=False

        setattr(djangoobject, fieldtochange, newvalue)

        try:

            djangoobject.save()

            print ": Success. Saved:",change,"to",newvalue

            print ": New Object:",djangoobject

            changelist.append(change)

            print "ChangeList:",changelist

        except:

            print "***Save Failed.",sys.exc_info()[0]

            ans=raw_input("Press 'Enter' to continue ... ")

        if editonerecord:

            ok=False

    return changelist

 

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