filterd_tracks.rb

def filtered_tracks(current_user)
  tracks = current_user.tracks.limit(500)
  rules = filters['rules']

  if rules.find {|h| h['id'] == 'track_name'}.present?
    track_name = rules.find {|h| h['id'] == 'track_name'}['value']

    tracks = tracks.where('tracks.name ILIKE ?', '%' + track_name + '%')
  end
  
  if rules.find {|h| h['id'] == 'artist_name'}.present?
    artist_name = rules.find {|h| h['id'] == 'artist_name'}['value']
    
    tracks = tracks.joins(:artist).where('artists.name ILIKE ?', '%' + artist_name + '%')
  end

  tracks
end

Which should take precedence? Right now, artist rules will override track name rules.

Assuming you want that to continue, maybe something like this (whether its better or not is your call):

artist_name = rules.find {|h| h['id'] == 'artist_name'}.to_h['value'] # to_h to handle nil
track_name = rules.find {|h| h['id'] == 'track_name'}.to_h['value'] unless artist_name
if artist_name
  tracks.joins(:artist).where('artists.name ILIKE ?', '%' + artist_name + '%')
elsif track_name
  tracks.where('tracks.name ILIKE ?', '%' + track_name + '%')
else 
  tracks
end

This is all roughly pseudo-code. There are other nips and tucks you could do, too (like going with more of a return ... if ... pattern if that floats your boat).

Your mileage/taste in code may vary.

@dummied: This is essentially outputting a query builder. So each tracks call tacks on a new where query, essentially.

Doing these bits over and over (there will be dozens of these if statements), feels...not correct.

if rules.find {|h| h['id'] == 'track_name'}.present?
    track_name = rules.find {|h| h['id'] == 'track_name'}['value']

def filtered_tracks(current_user)
  tracks = current_user.tracks.limit(500)
  rules = filters['rules']

  rules.find {|h| h['id'] == 'track_name'}.try do |rule|
    tracks = tracks.where('tracks.name ILIKE ?', '%' + rule['value'] + '%')
  end
  
  rules.find {|h| h['id'] == 'artist_name'}.try do |rule|
    tracks = tracks.joins(:artist).where('artists.name ILIKE ?', '%' + rule['value'] + '%')
  end

  tracks
end

Enumerable#find returns the matching result (or nil). Object#try runs the code in the block (yielding the object to the block), unless the object is nil (in which case it does nothing).

[1] pry(main)> rules = [ {'id' => "track_name", 'value' => "a"}, {'id' => "artist_name", 'value' => "b" }]
=> [{"id"=>"track_name", "value"=>"a"}, {"id"=>"artist_name", "value"=>"b"}]
[2] pry(main)> rules.find{|h| h["id"] == "track_name"}.try{|rule| "Add Rule: " +rule["value"] }
=> "Add Rule: a"
[3] pry(main)> rules.find{|h| h["id"] == "beats_per_minute"}.try{|rule| "Add Rule: " +rule["value"] }
=> nil

You could also consider extracting a method like:

def find_rule(rules, rule_name)
  rules.find{|r| r['id'] == rule_name}
end

if you don't want to keep typing r["id"] == "blah"

def filtered_tracks(current_user)
  tracks = current_user.tracks.limit(500)
  rules = filters['rules']

  find_rule(rules, 'track_name').try do |rule|
    tracks = tracks.where('tracks.name ILIKE ?', '%' + rule['value'] + '%')
  end
  
  find_rule(rules, 'artist_name').try do |rule|
    tracks = tracks.joins(:artist).where('artists.name ILIKE ?', '%' + rule['value'] + '%')
  end

  tracks
end

def find_rule(rules, rule_name)
  rules.find{|r| r['id'] == rule_name}
end