mildmojo · April 5, 2024 16:00 · Sep 28, 2017 · Jan 18, 2016 · Aug 31, 2015 · Oct 3, 2012
diff --git a/left_join_arel_example.rb b/left_join_arel_example.rb
@@ -1,6 +1,10 @@
 # Here's a contrived example of a LEFT JOIN using ARel. This is an example of
 # the mechanics, not a real-world use case.
 
+# NOTE: In the gist comments, @ozydingo linked their general-purpose ActiveRecord
+# extension that works for any named association. That's what I really wanted!
+# Go use that! Go: https://gist.github.com/ozydingo/70de96ad57ab69003446
+
 # == DEFINITIONS
 # - A Taxi is a car for hire. A taxi has_many :passengers.
 # - A Passenger records one person riding in one taxi one time. It belongs_to :taxi.

diff --git a/left_join_arel_example.rb b/left_join_arel_example.rb
@@ -9,7 +9,7 @@ class Taxi < ActiveRecord::Base
   # This scope LEFT JOINs the Passenger table. You might use this if you wanted
   # to select taxis by a set of taxi and passenger IDs (as with the
   # SQL "taxis.id IN () OR passengers.id IN ()").
-  def left_join_passengers
+  def self.left_join_passengers
     taxis = Taxi.arel_table
     passengers = Passenger.arel_table
 

diff --git a/left_join_arel_example.rb b/left_join_arel_example.rb
@@ -22,4 +22,7 @@ def left_join_passengers
                             join_sources
     joins(taxi_passengers)
   end
-end
+end
+
+# Sources that almost documented this:
+# http://blog.donwilson.net/2011/11/constructing-a-less-than-simple-query-with-rails-and-arel/
diff --git a/left_join_arel_example.rb b/left_join_arel_example.rb
@@ -2,7 +2,7 @@
 # the mechanics, not a real-world use case.
 
 # == DEFINITIONS
-# - A Taxi is a car for hire. A taxi has_many :passengers, class_name: 'Passenger'.
+# - A Taxi is a car for hire. A taxi has_many :passengers.
 # - A Passenger records one person riding in one taxi one time. It belongs_to :taxi.
 
 class Taxi < ActiveRecord::Base

diff --git a/gistfile1.rb → left_join_arel_example.rb b/gistfile1.rb → left_join_arel_example.rb
diff --git a/gistfile1.rb b/gistfile1.rb
@@ -2,24 +2,24 @@
 # the mechanics, not a real-world use case.
 
 # == DEFINITIONS
-# - A Taxi is a car for hire. A taxi has_many :riders, class_name: 'RiderHistory'.
+# - A Taxi is a car for hire. A taxi has_many :passengers, class_name: 'Passenger'.
 # - A Passenger records one person riding in one taxi one time. It belongs_to :taxi.
 
 class Taxi < ActiveRecord::Base
-  # This scope LEFT JOINs the RiderHistory table. You might use this if
-  # you wanted to select taxis by a set of taxi and passenger IDs (as with the
+  # This scope LEFT JOINs the Passenger table. You might use this if you wanted
+  # to select taxis by a set of taxi and passenger IDs (as with the
   # SQL "taxis.id IN () OR passengers.id IN ()").
-  def left_join_riders
+  def left_join_passengers
     taxis = Taxi.arel_table
-    passengers = Passengers.arel_table
+    passengers = Passenger.arel_table
 
     # The key here is providing the join type (Arel::Nodes::OuterJoin) and
     # grabbing the ARel join object itself from Arel::SelectManager#join_sources
     # to feed to ActiveRecord's #joins method.
     # SQL equivalent: "LEFT OUTER JOIN passengers ON taxis.id = passengers.taxi_id"
-    taxi_riders = taxis.join(passengers, Arel::Nodes::OuterJoin).
-                        on(taxis[:id].eq(passengers[:taxi_id])).
-                        join_sources
-    joins(taxi_riders)
+    taxi_passengers = taxis.join(passengers, Arel::Nodes::OuterJoin).
+                            on(taxis[:id].eq(passengers[:taxi_id])).
+                            join_sources
+    joins(taxi_passengers)
   end
 end
diff --git a/gistfile1.rb b/gistfile1.rb
@@ -0,0 +1,25 @@
+# Here's a contrived example of a LEFT JOIN using ARel. This is an example of
+# the mechanics, not a real-world use case.
+
+# == DEFINITIONS
+# - A Taxi is a car for hire. A taxi has_many :riders, class_name: 'RiderHistory'.
+# - A Passenger records one person riding in one taxi one time. It belongs_to :taxi.
+
+class Taxi < ActiveRecord::Base
+  # This scope LEFT JOINs the RiderHistory table. You might use this if
+  # you wanted to select taxis by a set of taxi and passenger IDs (as with the
+  # SQL "taxis.id IN () OR passengers.id IN ()").
+  def left_join_riders
+    taxis = Taxi.arel_table
+    passengers = Passengers.arel_table
+
+    # The key here is providing the join type (Arel::Nodes::OuterJoin) and
+    # grabbing the ARel join object itself from Arel::SelectManager#join_sources
+    # to feed to ActiveRecord's #joins method.
+    # SQL equivalent: "LEFT OUTER JOIN passengers ON taxis.id = passengers.taxi_id"
+    taxi_riders = taxis.join(passengers, Arel::Nodes::OuterJoin).
+                        on(taxis[:id].eq(passengers[:taxi_id])).
+                        join_sources
+    joins(taxi_riders)
+  end
+end
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