Many-to-many Association with HABTM

Rails
1

hey guys,

Basically i’ve already setup a many-to-many relationship between the 2
models and setup a Intermediate join Table without a primary_key on
the join table.

so i’ve done this

class Student < ActiveRecord::Base
has_and_belongs_to_many :teachers
end

and

class Teachers < ActiveRecord::Base
has_and_belongs_to_many :students
end

i’ve also created the following table

students_teachers

with the columns teacher_id and student_id

however when I try to create a student (logged in as the teacher
trying to create student record)

Where in the Student#Create Controller i am doing

@teacher = Teacher.where([‘id=?’,
session[:logged_teacher].techerId]).first
@student = @teacher.students.build(params[:student])

however when I try to create the user and save in the database the
record is being created in the student table however the Join Table is
not being populated. Am I doing something wrong here? am I missing
out on something?

Thx

2

use have many through is better and easier

3

On 6 November 2010 07:55, Zack [email protected] wrote:

Where in the Student#Create Controller i am doing

@teacher = Teacher.where([‘id=?’,
session[:logged_teacher].techerId]).first
@student = @teacher.students.build(params[:student])

however when I try to create the user and save in the database the
record is being created in the student table however the Join Table is
not being populated. Am I doing something wrong here? am I missing
out on something?

Do you save the @teacher after you’ve built the @student?
Your code all looks okay at first glance and seems to match what the
docs say:

But there is possible typo in there:
@teacher = Teacher.where([‘id=?’,
session[:logged_teacher].techerId]).first

…should that be “teacher_id” rather than “techerId”?
and you could just do @teacher =
Teacher.find(session[:logged_teacher].techerId)

As and aside, I’d recommend not saving whole Teacher objects in the
session - rather, just save their ID and retrieve them again from the
DB on the next request. I’ve seen problems in applications where one
too many objects gets saved in the session for the available space,
and much confusion ensues! :slight_smile: