Adding the possibility to build a closure from an ObjectiveC block.

base/mac/bind_objc_block.mm

Index: base/mac/bind_objc_block.mm
diff --git a/base/mac/bind_objc_block.mm b/base/mac/bind_objc_block.mm
new file mode 100644
index 0000000000000000000000000000000000000000..81472d09d25764e04a289f14d5885213d503afec
--- /dev/null
+++ b/base/mac/bind_objc_block.mm
@@ -0,0 +1,26 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "base/mac/bind_objc_block.h"
+
+#include "base/bind.h"
+#include "base/memory/scoped_nsobject.h"
+
+namespace {
+
+// Run the block contained in the parameter.
+void RunBlock(scoped_nsobject<id> block) {
+  void(^extracted_block)() = block.get();
+  extracted_block();
+}

[Mark Mentovai, 2012/07/25 15:40:19]

Won’t the scoped_nsobject<> destructor run here, doing [block release]?

[stuartmorgan, 2012/07/25 15:56:31]

Bind is hard for mortals to understand, but AFAICT what happens in that the
closure will have a copy of the scoped_nsobject (and thus a retain), and then
every call to RunBlock will (since it's pass-by-value) copy the scoped_nsobject,
thus creating a retain at the start of the function call, and that's the one
that's being released conceptually at this point.

When nothing owns the closure any more, *that's* when the [block copy] below is
balanced with a release.

+
+}  // namespace
+
+namespace base {
+
+base::Closure BindBlock(void(^block)()) {
+  return base::Bind(&RunBlock, scoped_nsobject<id>([block copy]));
+}
+
+}  // namespace base