Define state constants

README.md

@@ -366,6 +366,16 @@ Machine.successors
 }
 ```
 
+## Class constants
+Each machine's state will turn into a constant:
+```ruby
+Machine.state(:some_state, initial: true)
+Machine.state(:another_state)
+
+Machine::SOME_STATE #=> "some_state"
+Machine::ANOTHER_STATE # => "another_state"
+```
+
 ## Instance methods
 
 #### `Machine#current_state`

lib/statesman/machine.rb

@@ -39,6 +39,8 @@ def state(name, options = { initial: false })
           validate_initial_state(name)
           @initial_state = name
         end
+        define_state_constant(name)
+
         states << name
       end
 
@@ -163,6 +165,16 @@ def validate_from_and_to_state(from, to)
 
       private
 
+      def define_state_constant(state_name)
+        constant_name = state_name.upcase
+
+        if const_defined?(constant_name)
+          warn "Name conflict: '#{self.class.name}::#{constant_name}' is already defined"
+        else
+          const_set(constant_name, state_name)
+        end
+      end
+
       def add_callback(callback_type: nil, callback_class: nil,
                        from: nil, to: nil, &block)
         validate_callback_type_and_class(callback_type, callback_class)

spec/statesman/machine_spec.rb

@@ -13,10 +13,14 @@
 
     specify { expect(machine.states).to eq(%w[x y]) }
 
+    specify { expect(machine::X).to eq "x" }
+
+    specify { expect(machine::Y).to eq "y" }
+
     context "initial" do
-      before { machine.state(:x, initial: true) }
+      before { machine.state(:z, initial: true) }
 
-      specify { expect(machine.initial_state).to eq("x") }
+      specify { expect(machine.initial_state).to eq("z") }
 
       context "when an initial state is already defined" do
         it "raises an error" do
@@ -25,6 +29,15 @@
         end
       end
     end
+
+    context "when state name constant is already defined" do
+      it "warns about name conflict" do
+        machine.const_set(:SOME_CONST, "some const")
+        warning_message = "Name conflict: 'Class::SOME_CONST' is already defined\n"
+
+        expect { machine.state(:some_const) }.to output(warning_message).to_stderr
+      end
+    end
   end
 
   describe ".remove_state" do