CODEWITHSUNDEEP
djangodjango-modelsmany-to-many
fox
fox

Reputation: 16506

Complex lookup in django

I have a class that has a number of fields, two of which are many-to-many fields:

class someClass(models.Model):
    field1 = ...
    field2 = ...
    field3 = ...
    field4 = models.ManytoManyField(...)
    field5 = models.ManytoManyField(...)

I was originally hoping to use someClass.objects.get(...) later on:

someClass.objects.get(field1=..., field2=..., ...)

I would also like to limit the someClasses that get returned by field4 and field5 as well. I assume that I cannot do this in a .get() call because these represent many-to-many relationships that can take many forms.

At the time that I would have been looking to find a unique someClass, I would have access to several variables that correspond to objects represented in field1-field3, as well as two short lists of objects that correspond to the objects represented in field4 and in field5. These together should describe a unique instance.

Accepting that I may have to do this in a series of .filter()s, what is the best way for me to obtain the single someClass object that my data (again, one variable apiece for field1-field3 and two lists for field4 and field5) describes?

Upvotes: 2

Views: 119

Answers (1)

Yuji 'Tomita' Tomita
Yuji 'Tomita' Tomita

Reputation: 118458

I think the answer is as obvious as you expect...

You definitely can't use get here because of the m2ms - you have to chain the filters to exclude results that contain inexact m2m matches. 

query = someClass.objects.filter(field1=field1, field2=field2, field3=field3)

for item in list1:
   query = query.filter(foo=item)

for item in list2:
   query = query.filter(bar=item)

# substitute with fancy python as you wish.

Upvotes: 1

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