Add Invocation.invoke so we can access the result

lib/cc/service/invocation.rb

@@ -10,14 +10,16 @@ class CC::Service::Invocation
     error_handling: WithErrorHandling,
   }
 
+  attr_reader :result
+
   # Build a chain of invocation wrappers which eventually calls receive
   # on the given service, then execute that chain.
   #
   # Order is important. Each call to #with, wraps the last.
   #
   # Usage:
   #
-  #   CC::Service::Invocation.new(service) do |i|
+  #   CC::Service::Invocation.invoke(service) do |i|
   #     i.with :retries, 3
   #     i.with :metrics, $statsd
   #     i.with :error_handling, Rails.logger
@@ -28,12 +30,17 @@ class CC::Service::Invocation
   # metrics collector, then up again to the error handling. If the order
   # were reversed, the error handling middleware would prevent the other
   # middleware from seeing any exceptions at all.
+  def self.invoke(service, &block)
+    instance = new(service, &block)
+    instance.result
+  end
+
   def initialize(service)
     @chain = InvocationChain.new { service.receive }
 
     yield(self) if block_given?
 
-    @chain.call
+    @result = @chain.call
   end
 
   def with(middleware, *args)

test/invocation_test.rb

@@ -2,11 +2,12 @@
 
 class TestInvocation < Test::Unit::TestCase
   def test_success
-    service = FakeService.new
+    service = FakeService.new(:some_result)
 
-    CC::Service::Invocation.new(service)
+    result = CC::Service::Invocation.invoke(service)
 
     assert_equal 1, service.receive_count
+    assert_equal :some_result, result
   end
 
   def test_retries
@@ -15,7 +16,7 @@ def test_retries
     error_occurred = false
 
     begin
-      CC::Service::Invocation.new(service) do |i|
+      CC::Service::Invocation.invoke(service) do |i|
         i.with :retries, 3
       end
     rescue
@@ -29,7 +30,7 @@ def test_retries
   def test_metrics
     statsd = FakeStatsd.new
 
-    CC::Service::Invocation.new(FakeService.new) do |i|
+    CC::Service::Invocation.invoke(FakeService.new) do |i|
       i.with :metrics, statsd, "a_prefix"
     end
 
@@ -44,7 +45,7 @@ def test_metrics_on_errors
     error_occurred = false
 
     begin
-      CC::Service::Invocation.new(service) do |i|
+      CC::Service::Invocation.invoke(service) do |i|
         i.with :metrics, statsd, "a_prefix"
       end
     rescue
@@ -61,7 +62,7 @@ def test_error_handling
     service = FakeService.new
     service.raise_on_receive = true
 
-    CC::Service::Invocation.new(service) do |i|
+    CC::Service::Invocation.invoke(service) do |i|
       i.with :error_handling, logger, "a_prefix"
     end
 
@@ -74,7 +75,7 @@ def test_multiple_middleware
     service.raise_on_receive = true
     logger = FakeLogger.new
 
-    CC::Service::Invocation.new(service) do |i|
+    CC::Service::Invocation.invoke(service) do |i|
       i.with :retries, 3
       i.with :error_handling, logger
     end
@@ -89,7 +90,8 @@ class FakeService
     attr_reader :receive_count
     attr_accessor :raise_on_receive
 
-    def initialize
+    def initialize(result = nil)
+      @result = result
       @receive_count = 0
     end
 
@@ -99,6 +101,8 @@ def receive
       if @raise_on_receive
         raise "Boom"
       end
+
+      @result
     end
   end