Create a nicer interface for base::mac::GetValueFromDictionary

base/mac/foundation_util.h

 // Copyright (c) 2011 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.
 
 #ifndef BASE_MAC_FOUNDATION_UTIL_H_
 #define BASE_MAC_FOUNDATION_UTIL_H_
 #pragma once
 
 #include <CoreFoundation/CoreFoundation.h>
 
@@ skipping 84 matching lines @@
 //   |exec_name| - path to the binary
 //   returns - path to the application bundle, or empty on error
 BASE_EXPORT FilePath GetAppBundlePath(const FilePath& exec_name);
 
 // Utility function to pull out a value from a dictionary, check its type, and
 // return it.  Returns NULL if the key is not present or of the wrong type.
 BASE_EXPORT CFTypeRef GetValueFromDictionary(CFDictionaryRef dict,
                                              CFStringRef key,
                                              CFTypeID expected_type);
 
+// Utility function to pull out a value from a dictionary, check its type, and
+// return it.  Returns NULL if the key is not present or of the wrong type.
+BASE_EXPORT template<class T>
+T GetValueFromDictionary(CFDictionaryRef dict, CFStringRef key);

[Nico, 2011/11/11 23:08:36]

I don't understand why this is a template function instead of

GetCFStringFromDictionary();
GetCFNumberFromDictionary();

etc.

[KushalP, 2011/11/11 23:13:35]

I would've thought the template function is a cleaner way of using the method.

You can do something similar to your example with:

base::mac::GetValueFromDictionary<CFStringRef>();
base::mac::GetValueFromDictionary<CFNumberRef>();

+
 // Retain/release calls for memory management in C++.
 BASE_EXPORT void NSObjectRetain(void* obj);
 BASE_EXPORT void NSObjectRelease(void* obj);
 
 // CFTypeRefToNSObjectAutorelease transfers ownership of a Core Foundation
 // object (one derived from CFTypeRef) to the Foundation memory management
 // system.  In a traditional managed-memory environment, cf_object is
 // autoreleased and returned as an NSObject.  In a garbage-collected
 // environment, cf_object is marked as eligible for garbage collection.
 //
@@ skipping 143 matching lines @@
 
 BASE_EXPORT template<class T>
 T* ObjCCastStrict(id objc_val) {
   T* rv = ObjCCast<T>(objc_val);
   DCHECK(objc_val == nil || rv);
   return rv;
 }
 
 #endif  // defined(__OBJC__)
 
+// Utility function to pull out a value from a dictionary, check its type, and
+// return it.  Returns NULL if the key is not present or of the wrong type.
+// Is a cleaner implementation of base::mac::GetValueFromDictionary() above.
+BASE_EXPORT template<class T>
+T GetValueFromDictionary(CFDictionaryRef dict, CFStringRef key);
+
 }  // namespace mac
 }  // namespace base
 
 // Stream operations for CFTypes. They can be used with NSTypes as well
 // by using the NSToCFCast methods above.
 // e.g. LOG(INFO) << base::mac::NSToCFCast(@"foo");
 // Operator << can not be overloaded for ObjectiveC types as the compiler
 // can not distinguish between overloads for id with overloads for void*.
 BASE_EXPORT extern std::ostream& operator<<(std::ostream& o,
                                             const CFErrorRef err);
 BASE_EXPORT extern std::ostream& operator<<(std::ostream& o,
                                             const CFStringRef str);
 
 #endif  // BASE_MAC_FOUNDATION_UTIL_H_