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POJoin table attribute updates in Many-to-Many Relation
 

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  1. POJoin table attribute updates in Many-to-Many Relation
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    <p>I have a many-to-many relation setup for a data model which deals with a problem domain of Members and Addresses. Basically a 'member' can have multiple 'addresses', think of like when you have a work address and a home address. </p> <p>I want to store additional attributes on the join table and save data, apart from the foreign key attributes. There are many examples on the net about many-to-many relations, but I've not found details/examples on storing the extra data.</p> <p>Here is the problem that i'm stuck with.</p> <p>The models are setup as:</p> <p><strong>Models</strong></p> <pre><code>class Member &lt; ActiveRecord::Base has_many :member_addresses has_many :addresses, :through =&gt; :member_addresses end class MemberAddress &lt; ActiveRecord::Base belongs_to :address # foreign key for address -&gt; address_id belongs_to :member # foreign key for member -&gt;member_id end class Address &lt; ActiveRecord::Base has_many :member_addresses has_many :members, :through =&gt; :member_addresses accepts_nested_attributes_for :members, :allow_destroy =&gt; true end </code></pre> <p>The 'accepts_nested_attributes' on the Address class is for the nested-forms.</p> <p><strong>Database Schema/Migrations</strong> The tables (simplified for posting) are defined as</p> <pre><code>create_table "addresses", :force =&gt; true do |t| t.string "firstline" t.string "state" .... end create_table "member", :force =&gt; true do |t| t.string "name" .... end create_table "member_addresses", :force =&gt; true do |t| t.integer "member_id" t.integer "address_id" t.string "address_type" end </code></pre> <p>The field 'address_type' on the join table is intended for flagging the type of the address that is associated with the member (aka; "home" or "work")</p> <p><em><strong>It is updating this field that is where I'm getting stuck.</em></strong></p> <p><strong>Controllers &amp; View</strong></p> <p>The member_controller setups the model like:</p> <pre><code>members_controller.rb def new @member = Member.new @member.addresses.build #pre-build the associated address end </code></pre> <p>Then the view for the member page <strong>new</strong> action is</p> <p>&lt;%= form_for @member do |m| %></p> <pre><code> &lt;%= m.label :first_name, "First Name"%&gt; &lt;%= m.text_field :first_name %&gt; &lt;/p&gt; &lt;%= m.fields_for :addresses do |addrform|%&gt; &lt;%= addrform.label :firstline %&gt; &lt;%= addrform.text_field :firstline %&gt; &lt;% end %&gt; &lt;br /&gt; &lt;%= label_tag 'Type of address' %&gt; &lt;%= text_field_tag 'addrtype' %&gt; &lt;br /&gt; &lt;%= m.submit "Add" %&gt;&lt;br /&gt; </code></pre> <p>&lt;% end %></p> <p>The idea is that with the 'accepts_nested_attributes' on the <strong>Member</strong> model I can enter the data on the form to add in the name and address attributes. The additional <strong>label_tag</strong> is for the data to be posted for the address type that I want to store </p> <p>So when the form is filled in the post data (form a trap) looks like:</p> <pre><code>{"utf8"=&gt;"✓", "authenticity_token"=&gt;"E0R038rcdJmBGjjxQ9nQLHGVbzM4ejA0vsEaIvqkwkE=", "member"=&gt;{"first_name"=&gt;"James", "last_name"=&gt;"SMith", "addresses_attributes"=&gt;{"0"=&gt;{"firstline"=&gt;"this is the first line"}}}, "addrtype"=&gt;"home", "commit"=&gt;"Add"} </code></pre> <p>All good - i'm getting my <strong>Member</strong> data and the <strong>Address</strong> data, as well as the additional field 'addrtype' which is to be used for carrying my additional data</p> <p>Now how to get the data into the relation or join table ? On the <strong>member_controller create action</strong> </p> <pre><code>def create # create a member with the params posted @member = Member.new(params[:member]) # get data for 'relation data' @addr_type = params[:addrtype] if @member.save! #update the relation now created with the address type @member.member_addresses.first.address_type = @addr_type # save the relationship (is this necessary?) @member.save! redirect_to members_path end </code></pre> <p>As you can see in the <strong>create</strong> I'm attempting to fill in the data on the join table and then force a save again so that the relation or association with the additional attribute is saved. </p> <p>This doesn't work, and/or I'm doing it wrong.</p> <p>Any suggestions would be most appreciated.</p>
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