CODEWITHSUNDEEP
mysqldjangopython-2.7foreign-key-relationship
liloka
liloka

Reputation: 1016

Django Integrity Error - id cannot be null

I know this has been answered before, but I have been through every answer and nothing either makes sense or I feel like my code is already doing what is being said in the answers.

So I have a model for terms and links, which has a many-to-many relationship. 

class ProjectTerms(models.Model):
    id = models.IntegerField(primary_key=True) # AutoField?
    terms = models.CharField(max_length=100)

class Meta:
    db_table = 'project_terms'

class ProjectLinks(models.Model):
    id = models.IntegerField(primary_key=True) # AutoField?
    links = models.CharField(max_length=100)
    relations = models.ManyToManyField(ProjectTerms)

class Meta:
    db_table = 'project_links'

class ProjectLinksRelations(models.Model):
    id = models.IntegerField(primary_key=True) # AutoField?
    project_terms = models.ForeignKey('ProjectTerms')
    project_links = models.ForeignKey(ProjectLinks)

Script:

def create_models(my_term, my_link):
    saved_term = ProjectTerms.objects.update_or_create(terms = my_term)
    saved_link = ProjectLinks.objects.update_or_create(links = my_link)

    ProjectLinksRelations.objects.update_or_create(project_terms=saved_term, project_links=saved_link)

A lot of places say that the model (both term and link here) has to be saved before being added to the connecting database.

I've also tried creating each term and link separately and saving them like this:

def create_models(my_term, my_link):
    saved_term = ProjectTerms(terms = my_term)
    saved_term.save()
    saved_link = ProjectLinks(links = my_link)
    saved_link.save()

    relation = ProjectLinksRelations.objects.update_or_create(project_terms=saved_term, project_links=saved_link)
    relation.save()

Upvotes: 0

Views: 1211

Answers (1)

Peter DeGlopper
Peter DeGlopper

Reputation: 37319

All you need for this is:

class ProjectTerms(models.Model):
    terms = models.CharField(max_length=100)

class ProjectLinks(models.Model):
    links = models.CharField(max_length=100)
    relations = models.ManyToManyField(ProjectTerms)

The ID fields and the table for the ManyToManyField will be automatically created.

To set the ManyToMany relationship, use add:

def create_models(my_term, my_link):
    (saved_term, created) = ProjectTerms.objects.update_or_create(terms = my_term)
    (saved_link, created) = ProjectLinks.objects.update_or_create(links = my_link)
    saved_link.relations.add(saved_term)
    saved_link.save()

Upvotes: 1

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