updated edit form

app/views.py

@@ -85,19 +85,24 @@ def edit_book_by_id(id):
         if user_form.validate_on_submit():
             # check if the post request has the file part
             title = user_form.title.data # You could also have used request.form['name']
-            author = user_form.author.data # You could also have used request.form['email']
+            authors = user_form.author.data # You could also have used request.form['email']
             # save user to database
             #book = Book(title, author, filename, cover, file_extension)
-            book_to_edit.title = title
             db.session.commit()
 
-            book = Book.query.filter_by(title=title).first()
-            author_table = Author.query.filter_by(book_id=book.id).delete()
-            for this_author in author:
-                this_author = Author(this_author.get('author_name'))
-                book.authors.append(this_author)
-                db.session.commit()
-
+            book = Book.query.filter_by(id=id).first()
+            book.title = title
+            book.authors= []
+            db.session.commit()
+            for author in authors:
+                author_name = author.get("author_name")
+                if author_name:
+                    a = db.session.query(Author).filter_by(author_name=author_name).first()
+                    if a == None:
+                        a = Author(author_name=author_name)
+                        db.session.add(a)
+                    book.authors.append(a)
+            db.session.commit()
             flash("%s updated" % (title))
             return redirect(url_for('show_books'))