[Author: dmaclach]

Added some basic casting debugging goodness to GTM.
Opinions? added to help catch a bug in QSB.

R=thomasvl
DELTA=55  (55 added, 0 deleted, 0 changed)

1 files changed, 81 insertions, 0 deletions

diff --git a/DebugUtils/GTMTypeCasting.h b/DebugUtils/GTMTypeCasting.h
new file mode 100644
index 0000000..1e9ebb9
--- /dev/null
+++ b/DebugUtils/GTMTypeCasting.h
@@ -0,0 +1,81 @@
+//
+//  GTMTypeCasting.h
+//  
+//  Copyright 2010 Google Inc.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License"); you may not
+//  use this file except in compliance with the License.  You may obtain a copy
+//  of the License at
+// 
+//  http://www.apache.org/licenses/LICENSE-2.0
+// 
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+//  License for the specific language governing permissions and limitations under
+//  the License.
+//
+
+#import <Foundation/Foundation.h>
+#import "GTMDefines.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// These are some basic macros for making down-casting safer in Objective C.
+// They are loosely based on the same cast types with similar names in C++.
+// A typical usage would look like this:
+//
+// Bar* b = [[Bar alloc] init];
+// Foo* a = GTM_STATIC_CAST(Foo, b);
+//
+// Note that it's GTM_STATIC_CAST(Foo, b) and not GTM_STATIC_CAST(Foo*, b).
+//
+// GTM_STATIC_CAST runs only in debug mode, and will assert if and only if:
+//   - object is non nil
+//   - [object isKindOfClass:[cls class]] returns nil
+//
+// otherwise it returns object.
+//
+// GTM_DYNAMIC_CAST runs in both debug and release and will return nil if
+//   - object is nil
+//   - [object isKindOfClass:[cls class]] returns nil
+//
+// otherwise it returns object.
+//
+
+// Support functions for dealing with casting.
+GTM_INLINE id GTMDynamicCastSupport(Class cls, id object) {
+  id value = nil;
+  if (object) {
+    _GTMDevAssert(cls, @"Nil Class");
+    if ([object isKindOfClass:cls]) {
+      value = object;
+    }
+  }
+  return value;
+}
+
+GTM_INLINE id GTMStaticCastSupport(Class cls, id object) {
+  id value = nil;
+  if (object) {
+    value = GTMDynamicCastSupport(cls, object);
+    _GTMDevAssert(value, @"Could not cast %@ to class %@", object, cls);
+  }
+  return value;
+}
+
+#ifndef GTM_STATIC_CAST
+  #ifdef DEBUG
+    #define GTM_STATIC_CAST(type, object) GTMStaticCastSupport([type class], \
+                                                               object)
+  #else
+    #define GTM_STATIC_CAST(type, object) ((type *) (object))
+  #endif
+#endif
+
+#ifndef GTM_DYNAMIC_CAST
+  #define GTM_DYNAMIC_CAST(type, object) GTMDynamicCastSupport([type class], \
+                                                               object)
+#endif