Implement User#<=> for easier sorting. [#18]

app/models/user.rb

@@ -37,19 +37,6 @@ def country
     return self.state.nil? ? nil : self.state.country
   end
 
-  # Returns the user's name as a string. Order can be :first_last (default) or :last_first. E-mail address will be returned if no name is specified.
-  def to_s(format = :first_last)
-    case format
-    when :first_last
-      str = [self.firstname, self.lastname].delete_if {|e| e.blank?}.join(' ')
-    when :last_first
-      str = [self.lastname, self.firstname].delete_if {|e| e.blank?}.join(', ')
-    else
-      raise ArgumentError, "format must be :first_last, :last_first, or blank"
-    end
-    str.blank? ? self.email : str
-  end
-
   def coords
     c = self[:coords]
     if c.nil?
@@ -67,6 +54,25 @@ def coords
     end
     c
   end
+
+  # Compares users by last name, first name, and e-mail address in that order.
+  # ['Smith', 'John', 'jsmith1@aol.com'] < ['Smith', 'John', 'jsmith2@aol.com']
+  def <=>(other)
+    [self.lastname, self.firstname, self.email] <=> [other.lastname, other.firstname, other.email]
+  end
+
+  # Returns the user's name as a string. Order can be :first_last (default) or :last_first. E-mail address will be returned if no name is specified.
+  def to_s(format = :first_last)
+    case format
+    when :first_last
+      str = [self.firstname, self.lastname].delete_if {|e| e.blank?}.join(' ')
+    when :last_first
+      str = [self.lastname, self.firstname].delete_if {|e| e.blank?}.join(', ')
+    else
+      raise ArgumentError, "format must be :first_last, :last_first, or blank"
+    end
+    str.blank? ? self.email : str
+  end
 
   ##### The stuff below here comes from restful_authentication.
 

spec/models/user_spec.rb

@@ -110,6 +110,25 @@
 describe User, "(instance properties)" do
   fixtures :users
 
+  describe "<=>" do
+    it "should be valid" do
+      User.new.should respond_to(:<=>)
+      User.method(:<=>).arity.should == 1
+    end
+
+    it "should sort on last name, first name, and e-mail address in that order" do
+      smith = u(['Smith', 'John', 'jsmith1@aol.com'])
+      (smith <=> u(['Smith', 'John', 'jsmith2@aol.com'])).should == -1
+      (smith <=> u(['Jones', 'Robert', 'rj123@gmail.com'])).should == 1
+      (smith <=> u(['Smith', 'Mary', 'aaa@aaa.com'])).should == -1
+    end
+
+    protected
+    def u(array)
+      User.new(:lastname => array[0], :firstname => array[1], :email => array[2])
+    end
+  end
+
   describe "to_s" do
     it "should return firstname or lastname if only one of these is defined, 'firstname lastname' if both are defined, or e-mail address if no name is defined" do
       @user = User.new