some drying up of boiler plate initialization and equality code

9 files changed, 55 insertions, 71 deletions

diff --git a/lib/arel/extensions/class.rb b/lib/arel/extensions/class.rb
index 09e6d86ed4..f37898e7d7 100644
--- a/lib/arel/extensions/class.rb
+++ b/lib/arel/extensions/class.rb
@@ -1,4 +1,30 @@
 class Class
+  def attributes(*attrs)
+    @attributes = attrs
+    attr_reader *attrs
+  end
+  
+  def deriving(*methods)
+    methods.each { |m| derive m }
+  end
+  
+  def derive(method_name)
+    methods = {
+      :initialize => "
+        def #{method_name}(#{@attributes.join(',')})
+          #{@attributes.collect { |a| "@#{a} = #{a}" }.join("\n")}
+        end
+      ",
+      :== => "
+        def ==(other)
+          #{name} === other &&
+          #{@attributes.collect { |a| "@#{a} == other.#{a}" }.join(" &&\n")}
+        end
+      "
+    }
+    class_eval methods[method_name], __FILE__, __LINE__
+  end
+  
   def hash_on(delegatee)
     define_method :eql? do |other|
       self == other
diff --git a/lib/arel/relations/operations/alias.rb b/lib/arel/relations/operations/alias.rb
index d14a51f67a..8ed33fc597 100644
--- a/lib/arel/relations/operations/alias.rb
+++ b/lib/arel/relations/operations/alias.rb
@@ -1,10 +1,8 @@
 module Arel
   class Alias < Compound
     include Recursion::BaseCase
+    attributes :relation
+    deriving :initialize
     alias_method :==, :equal?
-    
-    def initialize(relation)
-      @relation = relation
-    end
   end
 end
\ No newline at end of file
diff --git a/lib/arel/relations/operations/group.rb b/lib/arel/relations/operations/group.rb
index bc3a7f3437..22af2734a6 100644
--- a/lib/arel/relations/operations/group.rb
+++ b/lib/arel/relations/operations/group.rb
@@ -1,15 +1,11 @@
 module Arel
   class Group < Compound
-    attr_reader :groupings
+    attributes :relation, :groupings
+    deriving :==
 
-    def initialize(relation, *groupings)
-      @relation, @groupings = relation, groupings.collect { |g| g.bind(relation) }
-    end
-
-    def ==(other)
-      Group       === other          and
-      relation    ==  other.relation and
-      groupings   ==  other.groupings
+    def initialize(relation, *groupings, &block)
+      @relation = relation
+      @groupings = (groupings + (block_given?? [yield(self)] : [])).collect { |g| g.bind(relation) }
     end
 
     def aggregation?
diff --git a/lib/arel/relations/operations/join.rb b/lib/arel/relations/operations/join.rb
index acad75c817..01fa6da255 100644
--- a/lib/arel/relations/operations/join.rb
+++ b/lib/arel/relations/operations/join.rb
@@ -1,6 +1,7 @@
 module Arel
   class Join < Relation
-    attr_reader :join_sql, :relation1, :relation2, :predicates
+    attributes :join_sql, :relation1, :relation2, :predicates
+    deriving :==
     delegate :engine, :name, :to => :relation1
     hash_on :relation1
 
@@ -45,13 +46,6 @@ module Arel
     def join?
       true
     end
-    
-    def ==(other)
-      Join       === other             and
-      predicates ==  other.predicates  and
-      relation1  ==  other.relation1   and
-      relation2  ==  other.relation2
-    end
   end
   
   class Relation
diff --git a/lib/arel/relations/operations/order.rb b/lib/arel/relations/operations/order.rb
index ebb4dc0668..82924806e2 100644
--- a/lib/arel/relations/operations/order.rb
+++ b/lib/arel/relations/operations/order.rb
@@ -1,19 +1,16 @@
 module Arel
   class Order < Compound
-    attr_reader :orderings
+    attributes :relation, :orderings
+    deriving :==
     
-    def initialize(relation, *orderings)
-      @relation, @orderings = relation, orderings.collect { |o| o.bind(relation) }
+    def initialize(relation, *orderings, &block)
+      @relation = relation
+      @orderings = (orderings + (block_given?? [yield(self)] : [])).collect { |o| o.bind(relation) }
     end
 
+    # TESTME
     def orders
-      orderings + relation.orders
-    end
-    
-    def ==(other)
-      Order       === other          and
-      relation    ==  other.relation and
-      orderings   ==  other.orderings
+      (orderings + relation.orders).collect { |o| o.bind(self) }
     end
   end
 end
\ No newline at end of file
diff --git a/lib/arel/relations/operations/project.rb b/lib/arel/relations/operations/project.rb
index 0efc13bdb3..2be87fe694 100644
--- a/lib/arel/relations/operations/project.rb
+++ b/lib/arel/relations/operations/project.rb
@@ -1,9 +1,11 @@
 module Arel
   class Project < Compound
-    attr_reader :projections
+    attributes :relation, :projections
+    deriving :==
     
-    def initialize(relation, *projections)
-      @relation, @projections = relation, projections
+    def initialize(relation, *projections, &block)
+      @relation = relation
+      @projections = (projections + (block_given?? [yield(self)] : [])).collect { |p| p.bind(relation) }
     end
 
     def attributes
@@ -13,11 +15,5 @@ module Arel
     def aggregation?
       attributes.any?(&:aggregation?)
     end
-    
-    def ==(other)
-      Project  === other          and
-      relation    ==  other.relation and
-      projections ==  other.projections
-    end
   end
 end
\ No newline at end of file
diff --git a/lib/arel/relations/operations/skip.rb b/lib/arel/relations/operations/skip.rb
index 01ac4c7204..ea5df21f53 100644
--- a/lib/arel/relations/operations/skip.rb
+++ b/lib/arel/relations/operations/skip.rb
@@ -1,15 +1,6 @@
 module Arel
   class Skip < Compound
-    attr_reader :skipped
-
-    def initialize(relation, skipped)
-      @relation, @skipped = relation, skipped
-    end
-
-    def ==(other)
-      Skip        === other          and
-      relation    ==  other.relation and
-      skipped     ==  other.skipped
-    end
+    attributes :relation, :skipped
+    deriving :initialize, :==
   end
 end
\ No newline at end of file
diff --git a/lib/arel/relations/operations/take.rb b/lib/arel/relations/operations/take.rb
index 0a49891aee..095e430417 100644
--- a/lib/arel/relations/operations/take.rb
+++ b/lib/arel/relations/operations/take.rb
@@ -1,15 +1,6 @@
 module Arel
   class Take < Compound
-    attr_reader :taken
-
-    def initialize(relation, taken)
-      @relation, @taken = relation, taken
-    end
-
-    def ==(other)
-      Take        === other          and
-      relation    ==  other.relation and
-      taken       ==  other.taken
-    end
+    attributes :relation, :taken
+    deriving :initialize, :==
   end
 end
\ No newline at end of file
diff --git a/lib/arel/relations/operations/where.rb b/lib/arel/relations/operations/where.rb
index ba34846c04..9acb8ae3c6 100644
--- a/lib/arel/relations/operations/where.rb
+++ b/lib/arel/relations/operations/where.rb
@@ -1,21 +1,16 @@
 module Arel
   class Where < Compound
-    attr_reader :predicate
+    attributes :relation, :predicate
+    deriving :==
 
-    def initialize(relation, *predicates)
-      predicate = predicates.shift
+    def initialize(relation, *predicates, &block)
+      predicate = block_given?? yield(self) : predicates.shift
       @relation = predicates.empty?? relation : Where.new(relation, *predicates)
       @predicate = predicate.bind(@relation)
     end
 
     def wheres
       @wheres ||= (relation.wheres + [predicate]).collect { |p| p.bind(self) }
-    end    
-
-    def ==(other)
-      Where     === other          and
-      relation  ==  other.relation and
-      predicate ==  other.predicate
     end
   end
 end
\ No newline at end of file