Duplicating model instances and their related objects in Django / Algorithm for recusrively duplicating an object

Question

I\'ve models for Books, Chapters and Pages. They are all written by a User:

from django.db import models
         


        

Answer 1

I think you'd be happier with a simpler data model, also.

Is it really true that a Page is in some Chapter but a different book?

userMe = User( username="me" )
userYou= User( username="you" )
bookMyA = Book( userMe )
bookYourB = Book( userYou )

chapterA1 = Chapter( book= bookMyA, author=userYou ) # "me" owns the Book, "you" owns the chapter?

chapterB2 = Chapter( book= bookYourB, author=userMe ) # "you" owns the book, "me" owns the chapter?

page1 = Page( book= bookMyA, chapter= chapterB2, author=userMe ) # Book and Author aggree, chapter doesn't?

It seems like your model is too complex.

I think you'd be happier with something simpler. I'm just guessing at this, since I don't your know entire problem.

class Book(models.Model)
    name = models.CharField(...)

class Chapter(models.Model)
    name = models.CharField(...)
    book = models.ForeignKey(Book)

class Page(models.Model)
    author = models.ForeignKey('auth.User')
    chapter = models.ForeignKey(Chapter)

Each page has distinct authorship. Each chapter, then, has a collection of authors, as does the book. Now you can duplicate Book, Chapter and Pages, assigning the cloned Pages to the new Author.

Indeed, you might want to have a many-to-many relationship between Page and Chapter, allowing you to have multiple copies of just the Page, without cloning book and Chapter.