adding struct initializer for reuse later

lib/thermostat.rb

@@ -2,13 +2,14 @@
 
 class Thermostat
 
-  autoload :Config,          File.join('thermostat', 'config')
-  autoload :ConfigLoader,    File.join('thermostat', 'config_loader')
-  autoload :Fan,             File.join('thermostat', 'fan')
-  autoload :HeatPump,        File.join('thermostat', 'heat_pump')
-  autoload :InvalidSetpoint, File.join('thermostat', 'invalid_setpoint')
-  autoload :Sensor,          File.join('thermostat', 'sensor')
-  autoload :Zone,            File.join('thermostat', 'zone')
+  autoload :Config,            File.join('thermostat', 'config')
+  autoload :ConfigLoader,      File.join('thermostat', 'config_loader')
+  autoload :Fan,               File.join('thermostat', 'fan')
+  autoload :HeatPump,          File.join('thermostat', 'heat_pump')
+  autoload :InvalidSetpoint,   File.join('thermostat', 'invalid_setpoint')
+  autoload :Sensor,            File.join('thermostat', 'sensor')
+  autoload :StructInitializer, File.join('thermostat', 'struct_initializer')
+  autoload :Zone,              File.join('thermostat', 'zone')
 
   attr_reader :default_config
 

lib/thermostat/config.rb

@@ -1,6 +1,8 @@
 class Thermostat
   class Config < Struct.new(:cooldown_seconds, :initial_set_point, :max_set_point, :min_set_point)
 
+    include StructInitializer
+
     COOLDOWN_SECONDS  = 120
     INITIAL_SET_POINT = 23.9
     MAX_SET_POINT     = 26.7
@@ -11,15 +13,5 @@ def self.default_initial_set_point; INITIAL_SET_POINT; end
     def self.default_max_set_point;     MAX_SET_POINT;     end
     def self.default_min_set_point;     MIN_SET_POINT;     end
 
-
-    def initialize(*args)
-      opts = args.last.is_a?(Hash) ? args.pop : Hash.new
-      super
-      members.each do |k|
-        next if self.send(k)
-        self.send "#{k}=", (opts[k] || self.class.send("default_#{k}") )
-      end
-    end
-
   end
 end

lib/thermostat/struct_initializer.rb

@@ -0,0 +1,21 @@
+class Thermostat
+  module StructInitializer
+
+    def initialize(*args)
+      opts = args.last.is_a?(Hash) ? args.pop : Hash.new
+      super
+      members.each do |k|
+        next if self.send(k)
+        self.send "#{k}=", (opts[k] || default_value_for(k))
+      end
+    end
+
+  private
+
+    def default_value_for(key)
+      m = "default_#{key}".intern
+      self.class.respond_to?(m) ? self.class.send(m) : nil
+    end
+
+  end
+end

spec/cases/thermostat/struct_initializer_spec.rb

@@ -0,0 +1,25 @@
+class Llama < Struct.new(:length)
+  include Thermostat::StructInitializer
+  def self.default_length; 1; end
+end
+describe Thermostat::StructInitializer do
+
+  let(:default_length) { Llama.default_length }
+  let(:subject) { Llama.new length }
+
+  context 'when not initialized' do
+    let(:length) { nil }
+    it 'has a default length' do
+      expect( subject.length ).to eq(default_length)
+    end
+  end
+
+
+  context 'when initialized' do
+    let(:length) { 2 }
+    it 'overrides the default length' do
+      expect( subject.length ).to eq(length)
+    end
+  end
+
+end