Databases
StackOverflow2013
Postsdbo
POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
    primarykey
    data
    text
    <p>How can I encapsulate a set of operations (most of which are essentially .where(...)) and apply it to different models, in a way that some of the models may not implement some of the operations and should return empty collections. (non-essential code skipped)</p> <p>What I have designed (but not satisfied with):</p> <pre><code>class ActivityFinder def self.find(query, limit = nil) activities = get_activities(query) activities = activities.sort_by(&amp;:created_at).reverse // some-kind of merge-sort activities = activities.slice(0, limit) if limit.present? activities end private def self.get_activities(query) activities = [] activities += query.apply(ModelA) activities += query.apply(ModelB) activities += query.apply(ModelC) activities end end class ActivityQuery def created_before(time) @created_before = time self end def created_after(time) @created_after = time self end def apply(activity) activity = activity.where("#{activity.table_name}.created_at &lt; ?", @created_before) if @created_before.present? activity = activity.where("#{activity.table_name}.created_at &gt;= ?", @created_after) if @created_after.present? // more operations, not all of them are suported by ModelC rescue NoMethodError return [] end end </code></pre> <p>Usage</p> <pre><code>query = ActivityQuery.new.created_before(last_time).with_hash(...) activities = ActivityFinder.find(query) </code></pre> <p>What I don't like:</p> <ul> <li>the rescue for NoMethodError</li> <li>if different models has different name for the field, it has to be handled as a <code>case</code> statement in the query, coupling in this way the query object with each of the models</li> </ul> <p>So I'm searching for suggestions for better implementation</p> <p><strong>UPDATE</strong></p> <p>The problem is I want to pass any object that I got from an ActiveModel, e.g. ActiveRecord::Relation, so I can't just define a module with the methods (and override when needed) and include it in the models I'm using. The question is more to point in the right direction for a clean design, and not about implementation details, which I'll figure out somehow</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USMaxim Krizhanovsky
    1. USMaxim Krizhanovsky
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
      1. This table or related slice is empty.
      1. VTUpMod
    1. COinstead of rescuing NoMethodError, you could just do something like: def method_missing(ignored_method_name, *args); return []; end
      singulars
      1. POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
      1. USsockmonk
    2. COOverride the method_missing of an ActiveRecord's subclass?
      singulars
      1. POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
      1. USMaxim Krizhanovsky
    3. COWell, if you can't put the model specific code into the model (where it belongs), you'll end up with a tightly coupled class.
      singulars
      1. POQueryObject for Rails - how to encapsulate set of operations on ActiveRecord
      1. USStefan
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload