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

@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