How to match specific fields on models? - django

Question

I have model as below, I need to get bookname as ForeignKey and it works on Django Admin but I also need pageCount related with bookPageCount to auto determine on Django Admin or on add new record. When I add new log to ReadList I want pageCount to define automatically depending on record selected from Book;
class Book(models.Model):
bookname = models.CharField(max_length=200, verbose_name='Kitap Adı')
bookAuthor = models.CharField(max_length=100, verbose_name='Yazar Adı')
bookPublisher = models.CharField(max_length=100, verbose_name='Yayın Evi')
bookPageCount = models.PositiveIntegerField(verbose_name='Sayfa Sayısı')
bookAddDate = models.DateField(verbose_name='Kitaplığa Eklenme Tarihi')
class Meta:
verbose_name = 'Kitap'
verbose_name_plural = 'Kitaplar'
class ReadList(models.Model):
bookName = models.ForeignKey('kitaplik.Book.bookname', related_name='bookName', on_delete=models.CASCADE, verbose_name='Kitap Adı')
readerName = models.ForeignKey('ogrenciler.Students.studentName', on_delete=models.CASCADE, related_name='readerName', verbose_name='Okuyan Kişi')
dateOfRead = models.DateField(verbose_name='Okuma Tarihi')
pageCount = models.ForeignKey('kitaplik.Book.bookPageCount', related_name='pageCount', on_delete=models.PROTECT, verbose_name='Sayfa Sayısı')
class Meta:
verbose_name = 'Okuma Günlüğü'
After first answer I imported post_save and reciever to models.py and it is now like this;
class Book(models.Model):
bookname = models.CharField(max_length=200, verbose_name='Kitap Adı')
bookAuthor = models.CharField(max_length=100, verbose_name='Yazar Adı')
bookPublisher = models.CharField(max_length=100, verbose_name='Yayın Evi')
bookPageCount = models.PositiveIntegerField(verbose_name='Sayfa Sayısı')
bookAddDate = models.DateField(verbose_name='Kitaplığa Eklenme Tarihi')
class Meta:
verbose_name = 'Kitap'
verbose_name_plural = 'Kitaplar'
def __str__(self):
return self.bookname
class ReadList(models.Model):
bookName = models.ForeignKey('Book', related_name='book', on_delete=models.CASCADE, verbose_name='Kitap Adı')
readerName = models.ForeignKey('ogrenciler.Students', on_delete=models.CASCADE, related_name='readerName', verbose_name='Okuyan Kişi')
dateOfRead = models.DateField(verbose_name='Okuma Tarihi')
pageCount = models.PositiveIntegerField(verbose_name='Sayfa Sayısı',blank=True, null=True)
class Meta:
verbose_name = 'Okuma Günlüğü'
#receiver(post_save, sender=ReadList)
def get_pageCount(sender, instance, **kwargs):
instance.pageCount = instance.book.pageCount
instance.save

Answer 1

Maybe, can you write a more concise code, using the ForeignKey without repeating the fields.
class ReadList(models.Model):
book = models.ForeignKey('kitaplik.Book', related_name='book', on_delete=models.CASCADE, verbose_name='Kitap Adı')
readerName = models.ForeignKey('ogrenciler.Students.studentName', on_delete=models.CASCADE, related_name='readerName', verbose_name='Okuyan Kişi')
dateOfRead = models.DateField(verbose_name='Okuma Tarihi')
class Meta:
verbose_name = 'Okuma Günlüğü'
Next, you can use ReadList.book.pageCount in your views or in your template.
EDIT
If you want to store the value of book.pageCountas a separate value in your your ReadList object, you can launch a signal after each ReadList creation:
#receiver(post_save, sender=ReadList)
def get_pageCount(sender, instance, **kwargs):
instance.pageCount = instance.book.pageCount
instance.save