Changed Promise API to conform to execute-method pattern

lib/concurrent/promise.rb

@@ -34,15 +34,30 @@ def initialize(*args, &block)
 
       @lock = Mutex.new
       @handler = block || Proc.new{|result| result }
-      @state = :pending
-      @value = nil
-      @reason = nil
+      @state = :unscheduled
       @rescued = false
       @children = []
       @rescuers = []
+      @args = args
 
       init_obligation
-      realize(*args) if root?
+    end
+
+    # @return [Promise]
+    def execute
+      if root?
+        if compare_and_set_state(:pending, :unscheduled)
+          @chain.each { |c| c.state = :pending }
+          realize(*@args)
+        end
+      else
+        parent.execute
+      end
+      self
+    end
+
+    def self.execute(*args, &block)
+      new(*args, &block).execute
     end
 
     def rescued?
@@ -57,13 +72,15 @@ def rescued?
     #
     # @return [Promise] the new promise
     def then(&block)
+      block = Proc.new{ |result| result } if block.nil?
+
       child = @lock.synchronize do
-        block = Proc.new{|result| result } if block.nil?
         @children << Promise.new(self, &block)
         @children.last.on_reject(@reason) if rejected?
         push(@children.last)
         @children.last
       end
+
       return child
     end
 

spec/concurrent/event_machine_defer_proxy_spec.rb

@@ -140,7 +140,7 @@ module Concurrent
               EventMachine.run do
 
                 @a = @b = @c = nil
-                p = Promise.new(1, 2, 3) do |a, b, c|
+                p = Promise.execute(1, 2, 3) do |a, b, c|
                   @a, @b, @c = a, b, c
                 end
                 sleep(0.1)
@@ -155,7 +155,7 @@ module Concurrent
 
               EventMachine.run do
                 @expected = nil
-                Promise.new(10){|a| a * 2 }.then{|result| @expected = result}
+                Promise.new(10){|a| a * 2 }.then{|result| @expected = result}.execute
                 sleep(0.1)
                 @expected.should eq 20
 
@@ -168,7 +168,7 @@ module Concurrent
 
               EventMachine.run do
 
-                p = Promise.new(10){|a| a * 2 }.then{|result| result * 2}
+                p = Promise.execute(10){|a| a * 2 }.then{|result| result * 2}
                 sleep(0.1)
                 p.value.should eq 40
 
@@ -184,7 +184,7 @@ module Concurrent
 
               EventMachine.run do
 
-                p = Promise.new{ raise StandardError.new('Boom!') }
+                p = Promise.execute{ raise StandardError.new('Boom!') }
                 sleep(0.1)
                 p.reason.should be_a(Exception)
                 p.reason.should.to_s =~ /Boom!/
@@ -200,7 +200,7 @@ module Concurrent
               EventMachine.run do
 
                 @expected = nil
-                Promise.new{ raise StandardError }.
+                Promise.execute{ raise StandardError }.
                   on_error(StandardError){|ex| @expected = 1 }.
                   on_error(StandardError){|ex| @expected = 2 }.
                   on_error(StandardError){|ex| @expected = 3 }
@@ -217,7 +217,7 @@ module Concurrent
               EventMachine.run do
 
                 @expected = nil
-                Promise.new{ raise StandardError }.
+                Promise.execute{ raise StandardError }.
                   on_error(ArgumentError){|ex| @expected = ex }.
                   on_error(LoadError){|ex| @expected = ex }.
                   on_error(Exception){|ex| @expected = ex }