Rails：设计具有未知属性的模型

Question

In my app I have a model called Address . The address field therein is the only required field, but the model can have any number of different other attributes.

Addresses will be created by importing rows from a .csv file. The CSV has to have an address column but may have many others, and they can be anything else and therefore impossible to predict.

How can I store this information accurately without having to add new DB columns each time? Can I make something like an extra DB column that stores information from columns not in the model? Can I run queries on that field (albeit bastardized)? Finally, when exporting this information back into CSV can I export that extra information back out?

Answer 1

One way to solve this is to use Postgres as a database and have a table with 2 columns: address and data where data is of jsonb type. What that gives you is an ability to push arbitrary key/value data. You still can query it via SQL and have indexes on those fields.

Alternative would be to use a NoSQL database like Mongo or Couch.

Answer 2

You can store your data as JSON in any text type column.. and retrieve it like

<% @applicant_user_workflow_step.properties.each do |key, value| %>
      <tr>
        <td><strong><%= key %> </strong></td>
      </tr>
      <tr>
        <td><%= value %></td>
      </tr>
 <% end %>

or

<%= fields_for :properties, OpenStruct.new(@applicant_user_workflow_step.properties) do |builder| %>
      <% @workflow_step.fields.order(:order_value).each do |field| %>
        <div class="row">
          <% if field.field_type.eql?('rating') %>
            <%= render "applicants/fields/application_custom_rating/rating", field: field, f: builder %>
          <% else %>
            <%= render "applicants/fields/#{field.field_type}", field: field, f: builder %>
          <% end %>
        </div>
      <% end %>
    <% end %>

Openstruct allows you to access key as instance methods for a hash

or simplly follow this
blog: http://railscasts.com/episodes/403-dynamic-forms?view=asciicast
answer: Using Rails serialize to save hash to database