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[selectricity-live] / vendor / plugins / engines / lib / engines / ruby_extensions.rb

diff --git a/vendor/plugins/engines/lib/engines/ruby_extensions.rb b/vendor/plugins/engines/lib/engines/ruby_extensions.rb
new file mode 100644 (file)
index 0000000..189ca46
--- /dev/null
+++ b/vendor/plugins/engines/lib/engines/ruby_extensions.rb
@@ -0,0 +1,113 @@
+#--
+# Add these methods to the top-level module so that they are available in all
+# modules, etc
+#++
+class ::Module
+  # Defines a constant within a module/class ONLY if that constant does
+  # not already exist.
+  #
+  # This can be used to implement defaults in plugins/engines/libraries, e.g.
+  # if a plugin module exists:
+  #   module MyPlugin
+  #     default_constant :MyDefault, "the_default_value"
+  #   end
+  #
+  # then developers can override this default by defining that constant at
+  # some point *before* the module/plugin gets loaded (such as environment.rb)
+  def default_constant(name, value)
+    if !(name.is_a?(String) or name.is_a?(Symbol))
+      raise "Cannot use a #{name.class.name} ['#{name}'] object as a constant name"
+    end
+    if !self.const_defined?(name)
+      self.class_eval("#{name} = #{value.inspect}")
+    end
+  end
+  
+  # A mechanism for defining configuration of Modules. With this
+  # mechanism, default values for configuration can be provided within shareable
+  # code, and the end user can customise the configuration without having to
+  # provide all values.
+  #
+  # Example:
+  #
+  #  module MyModule
+  #    config :param_one, "some value"
+  #    config :param_two, 12345
+  #  end
+  #
+  # Those values can now be accessed by the following method
+  #
+  #   MyModule.config :param_one  
+  #     => "some value"
+  #   MyModule.config :param_two  
+  #     => 12345
+  #
+  # ... or, if you have overrriden the method 'config'
+  #
+  #   MyModule::CONFIG[:param_one]  
+  #     => "some value"
+  #   MyModule::CONFIG[:param_two]  
+  #     => 12345
+  #
+  # Once a value is stored in the configuration, it will not be altered
+  # by subsequent assignments, unless a special flag is given:
+  #
+  #   (later on in your code, most likely in another file)
+  #   module MyModule
+  #     config :param_one, "another value"
+  #     config :param_two, 98765, :force
+  #   end
+  #
+  # The configuration is now:
+  #
+  #   MyModule.config :param_one  
+  #     => "some value" # not changed
+  #   MyModule.config :param_two  
+  #     => 98765
+  #
+  # Configuration values can also be given as a Hash:
+  #
+  #   MyModule.config :param1 => 'value1', :param2 => 'value2'
+  #
+  # Setting of these values can also be forced:
+  #
+  #   MyModule.config :param1 => 'value3', :param2 => 'value4', :force => true
+  #
+  # A value of anything other than false or nil given for the :force key will
+  # result in the new values *always* being set.
+  def config(*args)
+    
+    raise "config expects at least one argument" if args.empty?
+    
+    # extract the arguments
+    if args[0].is_a?(Hash)
+      override = args[0][:force]
+      args[0].delete(:force)
+      args[0].each { |key, value| _handle_config(key, value, override)}
+    else
+      _handle_config(*args)
+    end
+  end
+  
+  private
+    # Actually set the config values
+    def _handle_config(name, value=nil, override=false)
+      if !self.const_defined?("CONFIG")
+        self.class_eval("CONFIG = {}")
+      end
+    
+      if value != nil
+        if override or self::CONFIG[name] == nil
+          self::CONFIG[name] = value 
+        end
+      else
+        # if we pass an array of config keys to config(),
+        # get the array of values back
+        if name.is_a? Array
+          name.map { |c| self::CONFIG[c] }
+        else
+          self::CONFIG[name]
+        end
+      end      
+    end
+end