How to make Django ManyToMany relationships explicit on the receiving model's end
Relationships, particularly ManyToMany, in Django have always bothered me somewhat. In particular, since the relationship is only defined in one of the models, you can't tell from looking at the paired model what other relationships it might be hiding.
For example, from the Django Documentation:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
toppings = models.ManyToManyField(Topping)
You can tell from looking at the code that I'd find out the relevant toppings for a pizza at Pizza.toppings. But you cannot tell that I would be able to tell what pizzas have a topping at Topping.Pizza_set--you have to look at the Pizza class to see this.
As a result, by looking at Toppings, I don't actually know the full range of fields that it has.
Is there any way around this or to make it more explicit? Or is there something that I'm missing?
python django django-models
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
add a comment |
Relationships, particularly ManyToMany, in Django have always bothered me somewhat. In particular, since the relationship is only defined in one of the models, you can't tell from looking at the paired model what other relationships it might be hiding.
For example, from the Django Documentation:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
toppings = models.ManyToManyField(Topping)
You can tell from looking at the code that I'd find out the relevant toppings for a pizza at Pizza.toppings. But you cannot tell that I would be able to tell what pizzas have a topping at Topping.Pizza_set--you have to look at the Pizza class to see this.
As a result, by looking at Toppings, I don't actually know the full range of fields that it has.
Is there any way around this or to make it more explicit? Or is there something that I'm missing?
python django django-models
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
Did you tryTopping.Pizza_set.all()?
– Victor Castillo Torres
Aug 8 '13 at 2:50
Topping.pizza_set.all()is how to get the actual pizzas, which is not the issue--the question is how to make it clear in the actual model that the way to get pizzas is by callingtopping.pizza_set.<something>.
– jdotjdot
Aug 8 '13 at 5:07
add a comment |
Relationships, particularly ManyToMany, in Django have always bothered me somewhat. In particular, since the relationship is only defined in one of the models, you can't tell from looking at the paired model what other relationships it might be hiding.
For example, from the Django Documentation:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
toppings = models.ManyToManyField(Topping)
You can tell from looking at the code that I'd find out the relevant toppings for a pizza at Pizza.toppings. But you cannot tell that I would be able to tell what pizzas have a topping at Topping.Pizza_set--you have to look at the Pizza class to see this.
As a result, by looking at Toppings, I don't actually know the full range of fields that it has.
Is there any way around this or to make it more explicit? Or is there something that I'm missing?
python django django-models
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
Relationships, particularly ManyToMany, in Django have always bothered me somewhat. In particular, since the relationship is only defined in one of the models, you can't tell from looking at the paired model what other relationships it might be hiding.
For example, from the Django Documentation:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
toppings = models.ManyToManyField(Topping)
You can tell from looking at the code that I'd find out the relevant toppings for a pizza at Pizza.toppings. But you cannot tell that I would be able to tell what pizzas have a topping at Topping.Pizza_set--you have to look at the Pizza class to see this.
As a result, by looking at Toppings, I don't actually know the full range of fields that it has.
Is there any way around this or to make it more explicit? Or is there something that I'm missing?
python django django-models
python django django-models
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
asked Aug 8 '13 at 2:45
jdotjdot
9,09474486
9,09474486
Did you tryTopping.Pizza_set.all()?
– Victor Castillo Torres
Aug 8 '13 at 2:50
Topping.pizza_set.all()is how to get the actual pizzas, which is not the issue--the question is how to make it clear in the actual model that the way to get pizzas is by callingtopping.pizza_set.<something>.
– jdotjdot
Aug 8 '13 at 5:07
add a comment |
Did you tryTopping.Pizza_set.all()?
– Victor Castillo Torres
Aug 8 '13 at 2:50
Topping.pizza_set.all()is how to get the actual pizzas, which is not the issue--the question is how to make it clear in the actual model that the way to get pizzas is by callingtopping.pizza_set.<something>.
– jdotjdot
Aug 8 '13 at 5:07
Did you try
Topping.Pizza_set.all() ?– Victor Castillo Torres
Aug 8 '13 at 2:50
Did you try
Topping.Pizza_set.all() ?– Victor Castillo Torres
Aug 8 '13 at 2:50
Topping.pizza_set.all() is how to get the actual pizzas, which is not the issue--the question is how to make it clear in the actual model that the way to get pizzas is by calling topping.pizza_set.<something>.– jdotjdot
Aug 8 '13 at 5:07
Topping.pizza_set.all() is how to get the actual pizzas, which is not the issue--the question is how to make it clear in the actual model that the way to get pizzas is by calling topping.pizza_set.<something>.– jdotjdot
Aug 8 '13 at 5:07
add a comment |
2 Answers
2
active
oldest
votes
This seems to be an unavoidable side effect of the DRY principle. I don't know of any way to declaratively show the symmetry in these relations (other than by commenting and such). If you really want to make things explicit you could put the relationship in its own table (which Django is doing behind the scenes anyway), like:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
class PizzaToppings(models.Model):
# '+' disables the reverse relationship
pizza = models.ForeignKey(Pizza, related_name='+')
topping = models.ForeignKey(Topping, related_name='+')
... but of course then you'd lose some of the convenience of the ORM.
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
add a comment |
Found a way on Django's forum (lost link, sorry)
class Topping(models.Model):
explicit_pizza_set = models.ManyToManyField(Pizza, through=Pizza.toppings.through, blank=True)
class Pizza(models.Model):
toppings = models.ManyToManyField(Topping)
answered Nov 11 at 23:12
Guillaume Lebreton
545516
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
This seems to be an unavoidable side effect of the DRY principle. I don't know of any way to declaratively show the symmetry in these relations (other than by commenting and such). If you really want to make things explicit you could put the relationship in its own table (which Django is doing behind the scenes anyway), like:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
class PizzaToppings(models.Model):
# '+' disables the reverse relationship
pizza = models.ForeignKey(Pizza, related_name='+')
topping = models.ForeignKey(Topping, related_name='+')
... but of course then you'd lose some of the convenience of the ORM.
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
add a comment |
This seems to be an unavoidable side effect of the DRY principle. I don't know of any way to declaratively show the symmetry in these relations (other than by commenting and such). If you really want to make things explicit you could put the relationship in its own table (which Django is doing behind the scenes anyway), like:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
class PizzaToppings(models.Model):
# '+' disables the reverse relationship
pizza = models.ForeignKey(Pizza, related_name='+')
topping = models.ForeignKey(Topping, related_name='+')
... but of course then you'd lose some of the convenience of the ORM.
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
add a comment |
This seems to be an unavoidable side effect of the DRY principle. I don't know of any way to declaratively show the symmetry in these relations (other than by commenting and such). If you really want to make things explicit you could put the relationship in its own table (which Django is doing behind the scenes anyway), like:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
class PizzaToppings(models.Model):
# '+' disables the reverse relationship
pizza = models.ForeignKey(Pizza, related_name='+')
topping = models.ForeignKey(Topping, related_name='+')
... but of course then you'd lose some of the convenience of the ORM.
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
This seems to be an unavoidable side effect of the DRY principle. I don't know of any way to declaratively show the symmetry in these relations (other than by commenting and such). If you really want to make things explicit you could put the relationship in its own table (which Django is doing behind the scenes anyway), like:
class Topping(models.Model):
# ...
class Pizza(models.Model):
# ...
class PizzaToppings(models.Model):
# '+' disables the reverse relationship
pizza = models.ForeignKey(Pizza, related_name='+')
topping = models.ForeignKey(Topping, related_name='+')
... but of course then you'd lose some of the convenience of the ORM.
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
answered Aug 8 '13 at 3:07
Kevin Christopher Henry
22.5k46361
22.5k46361
add a comment |
add a comment |
Found a way on Django's forum (lost link, sorry)
class Topping(models.Model):
explicit_pizza_set = models.ManyToManyField(Pizza, through=Pizza.toppings.through, blank=True)
class Pizza(models.Model):
toppings = models.ManyToManyField(Topping)
answered Nov 11 at 23:12
Guillaume Lebreton
545516
add a comment |
Found a way on Django's forum (lost link, sorry)
class Topping(models.Model):
explicit_pizza_set = models.ManyToManyField(Pizza, through=Pizza.toppings.through, blank=True)
class Pizza(models.Model):
toppings = models.ManyToManyField(Topping)
answered Nov 11 at 23:12
Guillaume Lebreton
545516
add a comment |
Found a way on Django's forum (lost link, sorry)
class Topping(models.Model):
explicit_pizza_set = models.ManyToManyField(Pizza, through=Pizza.toppings.through, blank=True)
class Pizza(models.Model):
toppings = models.ManyToManyField(Topping)
answered Nov 11 at 23:12
Guillaume Lebreton
545516
Found a way on Django's forum (lost link, sorry)
class Topping(models.Model):
explicit_pizza_set = models.ManyToManyField(Pizza, through=Pizza.toppings.through, blank=True)
class Pizza(models.Model):
toppings = models.ManyToManyField(Topping)
answered Nov 11 at 23:12
Guillaume Lebreton
545516
answered Nov 11 at 23:12
Guillaume Lebreton
545516
answered Nov 11 at 23:12
Guillaume Lebreton
545516
answered Nov 11 at 23:12
Guillaume Lebreton
545516
545516
add a comment |
add a comment |
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Did you try
Topping.Pizza_set.all()?– Victor Castillo Torres
Aug 8 '13 at 2:50
Topping.pizza_set.all()is how to get the actual pizzas, which is not the issue--the question is how to make it clear in the actual model that the way to get pizzas is by callingtopping.pizza_set.<something>.– jdotjdot
Aug 8 '13 at 5:07