Use Channel to convey data for on_update

lib/elevate/channel.rb

@@ -0,0 +1,19 @@
+module Elevate
+  # A simple unidirectional stream of data with a single consumer.
+  #
+  # @api private
+  class Channel
+    def initialize(block)
+      @target = block
+    end
+
+    # Pushes data to consumers immediately
+    #
+    # @return [void]
+    #
+    # @api private
+    def <<(obj)
+      @target.call(obj)
+    end
+  end
+end

lib/elevate/operation.rb

@@ -8,11 +8,11 @@ class ElevateOperation < NSOperation
     #   newly initialized instance
     #
     # @api private
-    def initWithTarget(target, args: args, update: update_callback)
+    def initWithTarget(target, args: args, channel: channel)
       if init
         @coordinator = IOCoordinator.new
         @context = TaskContext.new(target, args)
-        @update_callback = update_callback
+        @channel = WeakRef.new(channel)
       end
 
       self
@@ -29,15 +29,6 @@ def cancel
       super
     end
 
-    def invoke_update_callback(args)
-      unless NSThread.isMainThread
-        performSelectorOnMainThread(:"invoke_update_callback:", withObject: args, waitUntilDone: true)
-        return
-      end
-
-      @update_callback.call(*args)
-    end
-
     # Runs the specified task.
     #
     # @return [void]
@@ -49,7 +40,7 @@ def main
       begin
         unless @coordinator.cancelled?
           @result = @context.execute do |*args|
-            invoke_update_callback(args) if @update_callback
+            @channel << args if @channel
           end
         end
 
@@ -60,7 +51,6 @@ def main
       @coordinator.uninstall
 
       @context = nil
-      @update_callback = nil
     end
 
     # Returns the exception that terminated this task, if any.

lib/elevate/task.rb

@@ -4,6 +4,7 @@ def initialize(controller, active_tasks, body)
       @controller = WeakRef.new(controller)
       @active_tasks = active_tasks
       @operation = nil
+      @channel = Channel.new(method(:on_update))
 
       @body = body
       @on_start = nil
@@ -30,7 +31,7 @@ def on_update=(block)
     end
 
     def start(args)
-      @operation = ElevateOperation.alloc.initWithTarget(@body, args: args, update: method(:on_update))
+      @operation = ElevateOperation.alloc.initWithTarget(@body, args: args, channel: @channel)
 
       @operation.addObserver(self, forKeyPath: "isFinished", options: NSKeyValueObservingOptionNew, context: nil)
       queue.addOperation(@operation)
@@ -58,20 +59,16 @@ def observeValueForKeyPath(path, ofObject: operation, change: change, context: c
     end
 
     def on_start
-      autorelease_pool do
-        if @on_start
-          @controller.instance_eval(&@on_start)
-          @on_start = nil
-        end
+      if @on_start
+        @controller.instance_eval(&@on_start)
+        @on_start = nil
       end
     end
 
     def on_finish
-      autorelease_pool do
-        if @on_finish
-          @controller.instance_exec(@operation.result, @operation.exception, &@on_finish)
-          @on_finish = nil
-        end
+      if @on_finish
+        @controller.instance_exec(@operation.result, @operation.exception, &@on_finish)
+        @on_finish = nil
       end
 
       @operation.removeObserver(self, forKeyPath: "isFinished")
@@ -80,7 +77,12 @@ def on_finish
       @active_tasks.delete(self)
     end
 
-    def on_update(*args)
+    def on_update(args)
+      unless NSThread.isMainThread
+        performSelectorOnMainThread(:"on_update:", withObject: args, waitUntilDone: false)
+        return
+      end
+
       @controller.instance_exec(*args, &@on_update) if @on_update
     end
   end

spec/operation_spec.rb

@@ -1,7 +1,7 @@
 describe Elevate::ElevateOperation do
   before do
     @target = lambda { @result }
-    @operation = Elevate::ElevateOperation.alloc.initWithTarget(@target, args: {}, update: nil)
+    @operation = Elevate::ElevateOperation.alloc.initWithTarget(@target, args: {}, channel: nil)
     @queue = NSOperationQueue.alloc.init
   end
 
@@ -55,7 +55,7 @@
     describe "when an exception is raised" do
       it "returns the exception" do
         @target = lambda { raise IndexError }
-        @operation = Elevate::ElevateOperation.alloc.initWithTarget(@target, args: {}, update: nil)
+        @operation = Elevate::ElevateOperation.alloc.initWithTarget(@target, args: {}, channel: nil)
 
         @queue.addOperation(@operation)
         @operation.waitUntilFinished()
@@ -68,7 +68,7 @@
   describe "#result" do
     before do
       @target = lambda { 42 }
-      @operation = Elevate::ElevateOperation.alloc.initWithTarget(@target, args: {}, update: nil)
+      @operation = Elevate::ElevateOperation.alloc.initWithTarget(@target, args: {}, channel: nil)
     end
 
     describe "before starting the operation" do
@@ -97,35 +97,4 @@
       end
     end
   end
-
-  describe "update_callback" do
-    before do
-      @yielded = {}
-
-      @callback = lambda do |arg|
-        @yielded[:thread] = NSThread.currentThread
-        @yielded[:args] = arg
-
-        Dispatch::Queue.main.async do
-          resume
-        end
-      end
-
-      @target = lambda { yield 42 }
-      @operation = Elevate::ElevateOperation.alloc.initWithTarget(@target, args: {}, update: @callback)
-      @queue.addOperation(@operation)
-    end
-
-    it "invokes the block on the UI thread" do
-      wait_max 0.5 do
-        @yielded[:thread].should == NSThread.mainThread
-      end
-    end
-
-    it "invokes the block with whatever was yielded" do
-      wait_max 0.5 do
-        @yielded[:args].should == 42
-      end
-    end
-  end
 end