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POHow to make database entries stick to a User's account if those entries were created before the User account was
 

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  1. POHow to make database entries stick to a User's account if those entries were created before the User account was
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    <p>I'm trying to think of the best way to allow users to create database objects without creating an account but then associating those objects with a user's account when they decide to sign up. I will describe an example application, how I would like it to behave, and the approaches I have come up with. I am looking for criticisms/enhancements to my approaches or a better approach purposed by one of you, my fellow programmers. </p> <h1>Example Application</h1> <p>Let's say we have a Rails application called <strong>Suggestion Box</strong>. This application allows users to visit the site and enter a suggestion. A <code>Suggestion</code> requires a description and an email address. The user does not need to be logged in. Here are the models:</p> <p><em>app/models/suggestion.rb</em></p> <pre><code>class Suggestion &lt; ActiveRecord::Base # == DB Columns # id :integer # user_id :integer # description :text # email :string belongs_to :user validates :description, :email, :presence =&gt; true end </code></pre> <p><em>app/models/user.rb</em></p> <pre><code>class User &lt; ActiveRecored::Base # == DB Columns # id :integer # name :string # email :string has_many :suggestions validates :name, :email, :presence =&gt; true end </code></pre> <h1>Use Case</h1> <p>Frank comes to the Suggestion Box application and enters in a suggestion. The next day Frank enters in another. If we ask the Rails console for all of suggestions we will get this:</p> <pre><code># rails console Suggestion.all =&gt; [#&lt;Suggestion id: 1, user_id: nil, email: "frank@example.com", description: "Don't worry"&gt;, #&lt;Suggestion id: 2, user_id: nil, email: "frank@example.com", description: "Be happy"&gt;] </code></pre> <p>On the third day Frank decides to bite the bullet and sign up for an account. He then creates another suggestion. At this point if we ask the console for <code>User</code> objects we get Frank:</p> <pre><code># rails console User.all =&gt; [#&lt;User id: 1, name: "Frank", email: "frank@example.com" &gt;] </code></pre> <p>If we ask for Frank's suggestions we get all 3 suggestions:</p> <pre><code># rails console frank = User.last =&gt; [#&lt;User id: 1, name: "Frank", email: "frank@example.com" &gt; frank.suggestions =&gt; #&lt;ActiveRecord::Associations::CollectionProxy [#&lt;Suggestion id: 1, user_id: nil, email: "frank@example.com", description: "Don't worry"&gt;, #&lt;Suggestion id: 2, user_id: nil, email: "frank@example.com", description: "Be happy"&gt;, #&lt;Suggestion id: 3, user_id: nil, email: "frank@example.com", description: "Don't worry be happy now!"&gt;] </code></pre> <p>Now how do we make this connection between Frank and his past suggestions automatic?</p> <h1>Approaches</h1> <h3>#1 Cookies</h3> <p>When a non logged in user submits a session I could store an indicator in a cookie about the created suggestions. Then when they sign up I could use this info to find the suggestions and assign them to the user. </p> <p>I don't really like this approach because it breaks down when the user accesses more than one device. </p> <h3>#2 After Create Callback</h3> <p>When a user signs up I could run an after create callback that would look like this:</p> <p><em>app/models.user.rb</em></p> <pre><code>class User &lt; ActiveRecored::Base ... after_create :assign_suggestions def assign_suggestions suggestions = Suggestion.where(:user_id =&gt; nil, :email =&gt; self.email) suggestions.each do |s| s.user = self s.save end end end </code></pre> <p>I really like this approach but there is one major downside. If Frank creates a fourth suggestion when not logged in it will not be added to his user object. To fix this I could write a callback on the <code>Suggestion</code> class that could check for matching emails.</p> <p><em>app/models/suggestion.rb</em></p> <pre><code>class Suggestion &lt; ActiveRecord::Base ... after_create :assign_users def assign_users if self.user.present? user = User.where(:email =&gt; self.email).first if user self.user = user end end end end </code></pre> <p>This is pretty good but if Frank creates a suggestion with a different email address (which could happen, I have many) then the suggestion will not be connected to Frank's user object.</p> <h1>Question</h1> <p>What do you guys think of Approach #2? (good or bad) Is there another trick on top of this I could use to connect Frank to suggestions he makes with other email addresses? Can you think of a different approach that would work better than mine?</p> <p>Thanks for the advice!</p>
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