Has_and_belongs_to_many relationship in nested forms

Rails
1

Hi,

I have two models (say model a and b) that are joined using the
has_and_belongs_to_many association. In model A I want to be able to
link
to model B in a form. But, when I create a nested_form for model B I
have a
problem. Instead of linking to the exciting records in Model B. It
creates
new ones. Is there anyway to use nested_forms so that model B objects
are
linked to, but not created on submission? When I create a new model A I
just want to link to, not create new model Bs. Is this possible?

Thanks,

Josh

2

On Wed, Mar 25, 2009 at 2:38 AM, Josh M. [email protected]
wrote:

Hi,

I have two models (say model a and b) that are joined using the
has_and_belongs_to_many association. In model A I want to be able to link
to model B in a form. But, when I create a nested_form for model B I have a
problem. Instead of linking to the exciting records in Model B. It creates
new ones. Is there anyway to use nested_forms so that model B objects are
linked to, but not created on submission? When I create a new model A I
just want to link to, not create new model Bs. Is this possible?

Yes, and it’s likely someone could help debug the issue if you post the
code.

–
Greg D.
http://destiney.com/

3

Here is the code. I am sorry because this is work I cannot post the
entire
application. Thanks for all help and I hope this makes my problem
clearer.

Thanks,

Josh

class StressTest < ActiveRecord::Base
has_and_belongs_to_many :tst_definitions
accepts_nested_attributes_for :tst_definitions
has_many :tst_datas
end

class StressTestsController < ApplicationController
layout ‘tests.html’
def index
@stress_tests = StressTest.all
end

def new
@stress_test = StressTest.new

#want to add not create new tst_definitions
@stress_test.tst_definitions<< TstDefinition.first

end

def create
@stress_test = StressTest.new(params[:stress_test])
logger.info params.to_yaml
if @stress_test.save
flash[:notice] = “Successfully create Stress Test:
#{@stress_test.name
}”
redirect_to :action => ‘index’
else
render :action => ‘new’
end
end

def destroy
@stress_test = StressTest.find(params[:id])
@stress_test.destroy
redirect_to :action => ‘index’
end
end

The new form
New Stress Test

<% form_for(@stress_test) do |f| %>

<%= f.label :name %> <%= f.text_field :name %>
<%= f.label :max_concurrent_scans %> <%= f.text_field :max_concurrent_scans %>
<%= f.label :number_of_runs %> <%= f.text_field :number_of_runs %>

<% f.fields_for :tst_definitions do |test_form| %>


  • <%= test_form.select :name, TstDefinition.find_by_sql(“select
    id,
    name from tst_definitions”).collect {|test| [test.name, test.id]} %> <%=
    link_to ‘Remove’, ‘#remove_project’, :class =>
    ‘remove_codesecure_project’
    %>


<%= link_to ‘Add a project’, ‘#add_project’, :class =>
‘add_codesecure_project’ %>
<% end -%>
<%= f.submit 'submit' %>

<% end -%>

Javascript that addess a new drop down so that multiple tst_definitions
can
be added to a single stress_test
$(document).ready(function() {
$(“a[class=“add_codesecure_project”]”).click(function(event){
var copy_object = $(“ul”).children().eq(0).clone()
copy_object.appendTo(“ul”);
var num_of_children = $(“ul”).children().size();
copy_object.children(“select”).attr(“id”,
copy_object.children(“select”).attr(“id”).replace(/0/, (num_of_children

1)));
copy_object.children(“select”).attr(“name”,
copy_object.children(“select”).attr(“name”).replace(/0/,
(num_of_children -
1)));
//alert(copy_object.children(“select”).attr(“id”).replace(/0/,
(num_of_children - 1)));

//alert(copy_object.children("select").attr("id"))
//alert(copy_object.attr("id"));

add_remove_link();

});

});

4

So how would you do something like this? I’m not sure whether I would
be better off going with accepts_nested_attributes_for
acts_as_taggable. My example is a habtm relationship between books
and authors. In a “new book” form, I would love to be able to connect
authors already existing in the database, but then being able to add a
new author if they don’t already exist. Thanks!

5

Hi, After I looked into it some more I figured it out. I had a little
bit
of a concept mix up with accepts_nested_attributes_for. Because I do
not
want to create nested record. I do not think it is appropriate for this
situation. So I do not use it anymore. Thanks for the help sorry to
cause
people trouble.

Josh