many-to-many

This is baffling me... When I save my model, the book objects are unchanged. But if I open the invoice and save it again, the changes are made. What am I doing wrong? class Invoice(models.Model): ... books = models.ManyToManyField(Book,blank=True,null=True) ... def save(self, *args, **kwargs): super(Invoice, self).save(*args, **kwargs) for book in self.books.all(): book.quantity -= 1 if book.quantity == 0: book.sold = True; book.save() Edit: I've tried using the post_save signal, but it works the same way. No changes on the first save, changes saved the second time. Update: Seems to be solved

When having a fully fledged many-to-many with all relations described, the deletion of one of the two main objects crashes. Description Car ( .car_ownerships ) <-> ( .car ) CarOwnership ( .person ) <-> ( .car_ownerships ) Person Car ( .people ) <-----------------> ( .cars ) Person Problem When deleting a Car or a Person SA first deletes the association object CarOwnership (because of the 'through' relationship with the secondary argument) and then tries to update the foreign keys to NULL in the same association objects, hence crashing. How should I solve this? I'm a little perplexed to see

I have a Person model that has a many-to-many relationship with an Email model and I want to create a factory that lets me generate a first and last name for the person (this is already done) and create an email address that is based off of that person's name. Here is what I have for create a person 's name: Factory.sequence :first_name do |n| first_name = %w[FirstName1 FirstName2] # ... etc (I'm using a real subset of first names) first_name[(rand * first_name.length)] end Factory.sequence :last_name do |n| last_name = %w[LastName1 LastName2] # ... etc (I'm using a real subset of last names)

We have 2 tables: Table Authority: public class Authority { public int ID {get;set;} public string Name{get;set;} ... } Table Agents public class Agent { public int ID{get;set;} public int FirstName{get;set;} } And we have a relationship many-to-many between these two tables: public class AuthorityConfiguration : EntityTypeConfiguration<Authority> { public AuthorityConfiguration() : base() { HasKey(p => p.ID); HasMany(p => p.Agents).WithMany(a => a.Authorities).Map(mc => { mc.MapLeftKey("AuthorityID"); mc.MapRightKey("AgentID"); mc.ToTable("AuthorityAgent"); }); ToTable("Authority"); } }

I have been trying to figure this one out for a few days now. I am using Rails 4 (with the updated mass assignment technique) and trying to use nested attributes with a many-to-many relationship. My record is saving to the DB but everything is nil and I'm getting an "Unpermitted parameters: school, alumnis, prospects" error in my logs. Here's what I have: referral.rb class Referral < ActiveRecord::Base belongs_to :school belongs_to :alumni belongs_to :prospect end alumni.rb class Alumni < ActiveRecord::Base has_many :referrals has_many :prospects, through: :referrals accepts_nested_attributes

Hi guys! Is possible to do this with only two Rails models, User and Event: Users |id |name |age | |1 |danilo |26 | |2 |joe |23 | |3 |carlos |50 | |4 |katy |45 | Events_Users |event_id |user_id |confirmed | |1 |1 |1 | |3 |3 |0 | |4 |3 |1 | |2 |3 |1 | Events |id |name |date | |1 |the end of the year |31/12/2012 | |2 |the end of the world |21/12/2012 | |3 |Party |18/12/2012 | |4 |Dinner |19/12/2012 | The problem is, the user can confirm or not their presence in an event, for this I used the table Events_Users, column confirmed (1 for confirmed). How can I do this with Rails ActiveRecord without

If I have a many-to-many relationship defined in EF: public class StudentImage { public int StudentId { get; set; } public int ImageId { get; set; } public int Order { get; set; } public virtual Student Student { get; set; } public virtual Image Image { get; set; } } public class Student { public int Id { get; set; } public string Name { get; set; } public virtual ICollection<StudentImage> Images { get; set; } } public class Image { public int Id { get; set; } public string Filename { get; set; } public virtual ICollection<StudentImage> Students { get; set; } } And the DTO's: public class