Rails 3 multiple parameter filtering using scopes

Question

Trying to do a basic filter in rails 3 using the url params. I'd like to have a white list of params that can be filtered by, and return all the items that match. I've set up some scopes (with many more to come):

# in the model:
scope :budget_min, lambda {|min| where("budget > ?", min)}
scope :budget_max, lambda {|max| where("budget < ?", max)}

...but what's the best way to use some, none, or all of these scopes based on the present params[]? I've gotten this far, but it doesn't extend to multiple options. Looking for a sort of "chain if present" type operation.

@jobs = Job.all
@jobs = Job.budget_min(params[:budget_min]) if params[:budget_min]

lucapette · Accepted Answer · 2011-11-29 19:11:29Z

6

I think you are close. Something like this won't extend to multiple options?

query = Job.scoped
query = query.budget_min(params[:budget_min]) if params[:budget_min]
query = query.budget_max(params[:budget_max]) if params[:budget_max]
@jobs = query.all

edited Nov 29, 2011 at 19:11

lucapette

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answered Nov 29, 2011 at 17:10

maxenglander

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1 Comment

brittohalloran Over a year ago

perfect - I was missing the Job.scoped

lucapette · Accepted Answer · 2011-11-29 16:38:40Z

1

Generally, I'd prefer hand-made solutions but, for this kind of problem, a code base could become a mess very quickly. So I would go for a gem like meta_search.

answered Nov 29, 2011 at 16:38

lucapette

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1 Comment

brittohalloran Over a year ago

looks interesting, but there's gotta be a simple way that doesn't require a tack on gem

ramblex · Accepted Answer · 2011-11-29 17:45:44Z

One way would be to put your conditionals into the scopes:

scope :budget_max, lambda { |max| where("budget < ?", max) unless max.nil? }

That would still become rather cumbersome since you'd end up with:

Job.budget_min(params[:budget_min]).budget_max(params[:budget_max]) ...

A slightly different approach would be using something like the following inside your model (based on code from here:

class << self
  def search(q)
    whitelisted_params = {
      :budget_max => "budget > ?",
      :budget_min => "budget < ?"
    }

    whitelisted_params.keys.inject(scoped) do |combined_scope, param|
      if q[param].nil?
        combined_scope
      else
        combined_scope.where(whitelisted_params[param], q[param])
      end
    end
  end
end

You can then use that method as follows and it should use the whitelisted filters if they're present in params:

MyModel.search(params)

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