Re work API to accept booleans and hashes.

Update readme to make demonstrate new api.

README.md

@@ -213,17 +213,17 @@ end
 `steady_state` also follows the same `prefix` api as `delegate` in Rails.  You may optionally define your scopes to be prefixed to the name of the state machine with `prefix: true`, or you may provide a custom prefix with `prefix: :some_custom_name`.  This may be useful when dealing with multiple state machines on one object.
 
 ```ruby
-steady_state :temperature, scopes: true, prefix: true do
+steady_state :temperature, scopes: { prefix: true } do
   state 'cold', default: true
 end
 
-steady_state :conductivity, scopes: true, prefix: :sigma do
-  state 'conductive', default: true
+steady_state :color_temperature, scopes: { prefix: 'color' } do
+  state 'cold', default: true
 end
 
 Material.solid # => query for 'solid' records
-Material.temperature_cold # => query for 'cold' records
-Material.sigma_conductive # => query for 'conductive' records
+Material.temperature_cold # => query for records with a cold temperature
+Material.color_cold # => query for for records with a cold color temperature
 ```
 
 ### Next and Previous States

lib/steady_state/attribute.rb

@@ -15,7 +15,7 @@ module Attribute
     end
 
     class_methods do
-      def steady_state(attr_name, predicates: true, states_getter: true, scopes: SteadyState.active_record?(self), prefix: false, &block) # rubocop:disable Metrics/
+      def steady_state(attr_name, predicates: true, states_getter: true, scopes: SteadyState.active_record?(self), &block) # rubocop:disable Metrics/
         overrides = Module.new do
           define_method :"validate_#{attr_name}_transition_to" do |next_value|
             if public_send(attr_name).may_become?(next_value)
@@ -55,15 +55,15 @@ def steady_state(attr_name, predicates: true, states_getter: true, scopes: Stead
         end
 
         delegate(*state_machines[attr_name].predicates, to: attr_name, allow_nil: true) if predicates
-
         if scopes
-          scope_prefix = if prefix
-                           "#{prefix == true ? attr_name : prefix}_"
-                         else
-                           ""
-                         end
+          prefix = if scopes == true
+                     ''
+                   elsif scopes.is_a?(Hash) && scopes[:prefix]
+                     "#{scopes[:prefix] == true ? attr_name : scopes[:prefix]}_"
+                   end
+
           state_machines[attr_name].states.each do |state|
-            scope :"#{scope_prefix}#{state}", -> { where(attr_name.to_sym => state) }
+            scope :"#{prefix}#{state}", -> { where(attr_name.to_sym => state) }
           end
         end
 

spec/steady_state/attribute_spec.rb

@@ -395,7 +395,7 @@ def self.scope(name, callable)
     end
 
     context 'enabled with prefix: true' do
-      let(:opts) { { scopes: true, prefix: true } }
+      let(:opts) { { scopes: { prefix: true } } }
 
       it 'defines a scope for each state, prefixed with the name of the state machine' do
         expect(steady_state_class.defined_scopes.keys).to eq %i(car_driving car_stopped car_parked)
@@ -410,7 +410,7 @@ def self.scope(name, callable)
     end
 
     context 'enabled with a custom prefix such as prefix: :automobile' do
-      let(:opts) { { scopes: true, prefix: :automobile } }
+      let(:opts) { { scopes: { prefix: :automobile } } }
 
       it 'defines a scope for each state with the custom prefix' do
         expect(steady_state_class.defined_scopes.keys).to eq %i(automobile_driving automobile_stopped automobile_parked)