Ok so this is probably a trivial question but I’m having trouble visualizing and understanding the differences and when to use each. I’m also a little unclear as to how concepts like uni-directional and bi-directional mappings affect the one-to-many/many-to-many relationships. I’m using Hibernate right now so any explanation that’s ORM related will be helpful. As … Read more
There is a handy dynamic attribute in active-record called find_or_create_by: Model.find_or_create_by_<attribute>(:<attribute> => “”) But what if I need to find_or_create by more than one attribute? Say I have a model to handle a M:M relationship between Group and Member called GroupMember. I could have many instances where member_id = 4, but I don’t ever want … Read more
When you have a many-to-many relationship (related_name, not through) and you are trying to use the admin interface you are required to enter one of the relationships even though it does not have to exist for you to create the first entry. I’m creating an app that is an event organizer. Imagine we had Event … Read more
I have this scenario: public class Member { public int MemberID { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public virtual ICollection<Comment> Comments { get; set; } } public class Comment { public int CommentID { get; set; } public string Message { get; set; … Read more
What is the related_name argument useful for on ManyToManyField and ForeignKey fields? For example, given the following code, what is the effect of related_name=”maps”? class Map(db.Model): members = models.ManyToManyField(User, related_name=”maps”, verbose_name=_(‘members’)) 6 s 6
