support reading from- and to-state during on_transition callback #100

CHANGELOG.md

@@ -10,6 +10,7 @@
  * allow configuring behavior of nested transactions (see [issue #107](https://github.com/aasm/aasm/issues/107))
  * support multiple guards per transition
  * support event guards (see [issue #85](https://github.com/aasm/aasm/issues/85))
+ * support reading from- and to-state during on_transition callback (see [issue #100](https://github.com/aasm/aasm/issues/100))
 
 ## 3.0.26
 

README.md

@@ -152,6 +152,15 @@ In this case the `set_process` would be called with `:defagmentation` argument.
 In case of an error during the event processing the error is rescued and passed to `:error`
 callback, which can handle it or re-raise it for further propagation.
 
+During the `:on_transition` callback (and reliably only then) you can access the
+originating state (the from-state) and the target state (the to state), like this:
+
+```ruby
+  def set_process(name)
+    logger.info "from #{aasm.from_state} to #{aasm.to_state}"
+  end
+```
+
 ### Guards
 
 Let's assume you want to allow particular transitions only if a defined condition is

lib/aasm/instance_base.rb

@@ -1,6 +1,8 @@
 module AASM
   class InstanceBase
 
+    attr_accessor :from_state, :to_state
+
     def initialize(instance)
       @instance = instance
     end

lib/aasm/transition.rb

@@ -41,6 +41,9 @@ module AASM
     private
 
     def _execute(obj, on_transition, *args)
+      obj.aasm.from_state = @from if obj.aasm.respond_to?(:from_state=)
+      obj.aasm.to_state = @to if obj.aasm.respond_to?(:to_state=)
+
       case on_transition
       when Proc
         on_transition.arity == 0 ? on_transition.call : on_transition.call(obj, *args)

spec/unit/transition_spec.rb

@@ -139,7 +139,7 @@ describe AASM::Transition, '- when executing the transition with a Proc' do
     opts = {:from => 'foo', :to => 'bar', :on_transition => Proc.new {|o| o.test}}
     st = AASM::Transition.new(opts)
     args = {:arg1 => '1', :arg2 => '2'}
-    obj = double('object')
+    obj = double('object', :aasm => 'aasm')
 
     expect(opts[:on_transition]).to receive(:call).with(any_args)
 
@@ -150,7 +150,7 @@ describe AASM::Transition, '- when executing the transition with a Proc' do
     opts = {:from => 'foo', :to => 'bar', :on_transition => Proc.new {||}}
     st = AASM::Transition.new(opts)
     args = {:arg1 => '1', :arg2 => '2'}
-    obj = double('object')
+    obj = double('object', :aasm => 'aasm')
 
     expect(opts[:on_transition]).to receive(:call).with(no_args)
 
@@ -163,7 +163,7 @@ describe AASM::Transition, '- when executing the transition with an :on_transtio
     opts = {:from => 'foo', :to => 'bar', :on_transition => 'test'}
     st = AASM::Transition.new(opts)
     args = {:arg1 => '1', :arg2 => '2'}
-    obj = double('object')
+    obj = double('object', :aasm => 'aasm')
 
     expect(obj).to receive(:test)
 
@@ -174,7 +174,7 @@ describe AASM::Transition, '- when executing the transition with an :on_transtio
     opts = {:from => 'foo', :to => 'bar', :on_transition => :test}
     st = AASM::Transition.new(opts)
     args = {:arg1 => '1', :arg2 => '2'}
-    obj = double('object')
+    obj = double('object', :aasm => 'aasm')
 
     expect(obj).to receive(:test)
 
@@ -185,7 +185,7 @@ describe AASM::Transition, '- when executing the transition with an :on_transtio
     opts = {:from => 'foo', :to => 'bar', :on_transition => :test}
     st = AASM::Transition.new(opts)
     args = {:arg1 => '1', :arg2 => '2'}
-    obj = double('object')
+    obj = double('object', :aasm => 'aasm')
 
     def obj.test(args)
       "arg1: #{args[:arg1]} arg2: #{args[:arg2]}"
@@ -200,7 +200,7 @@ describe AASM::Transition, '- when executing the transition with an :on_transtio
     opts = {:from => 'foo', :to => 'bar', :on_transition => :test}
     st = AASM::Transition.new(opts)
     args = {:arg1 => '1', :arg2 => '2'}
-    obj = double('object')
+    obj = double('object', :aasm => 'aasm')
 
     def obj.test
       'success'
@@ -211,4 +211,19 @@ describe AASM::Transition, '- when executing the transition with an :on_transtio
     expect(return_value).to eq('success')
   end
 
+  it 'should allow accessing the from_state and the to_state' do
+    opts = {:from => 'foo', :to => 'bar', :on_transition => :test}
+    st = AASM::Transition.new(opts)
+    args = {:arg1 => '1', :arg2 => '2'}
+    obj = double('object', :aasm => AASM::InstanceBase.new('object'))
+
+    def obj.test(args)
+      "from: #{aasm.from_state} to: #{aasm.to_state}"
+    end
+
+    return_value = st.execute(obj, args)
+
+    expect(return_value).to eq('from: foo to: bar')
+  end
+
 end