Add event resolver to projection

5cd0154#r100429552

Author: lukaszreszke

ruby_event_store/lib/ruby_event_store/projection.rb

@@ -4,20 +4,21 @@ module RubyEventStore
   class Projection
     private_class_method :new
 
-    def initialize(initial_state = nil)
+    def initialize(initial_state = nil, event_type_resolver)
       @handlers = {}
+      @event_type_resolver = event_type_resolver
       @init = -> { initial_state }
     end
 
-    def self.init(initial_state = nil)
-      new(initial_state)
+    def self.init(initial_state = nil, event_type_resolver: EventTypeResolver.new)
+      new(initial_state, event_type_resolver)
     end
 
     def on(*event_klasses, &block)
       raise(ArgumentError, 'No handler block given') unless block_given?
 
       event_klasses.each do |event_klass|
-        name = event_klass.to_s
+        name = @event_type_resolver.call(event_klass)
 
         @handlers[name] = ->(state, event) { block.call(state, event) }
       end

ruby_event_store/spec/projection_spec.rb

@@ -229,15 +229,29 @@ module RubyEventStore
       expect(state).to eq(initial_state)
     end
 
-    specify "events with event type defined as class method" do
+    specify "events with custom event type" do
+      class CustomResolver
+        def call(event)
+          event.resolves_as
+        end
+      end
+
       class Snowflake < Event
-        def self.event_type
+        def self.resolves_as
+          "snowflake"
+        end
+
+        def event_type
           "snowflake"
         end
       end
 
       class SnowflakeV2 < Event
-        def self.event_type
+        def self.resolves_as
+          "snowflake"
+        end
+
+        def event_type
           "snowflake"
         end
       end
@@ -247,9 +261,9 @@ def self.event_type
 
       state =
         Projection
-          .init({ snowflake: 0 })
+          .init({ snowflake: 0 }, event_type_resolver: CustomResolver.new)
           .on(Snowflake, SnowflakeV2) do |state, event|
-            state[event.class.event_type.to_sym] += event.data.fetch(:arms)
+            state[:snowflake] += event.data.fetch(:arms)
             state
           end
           .call(event_store.read.stream("snowflake$1"))