Question

这是你应该如何在ARC使用CFMutableDictionaryRef？

CFMutableDictionaryRef myDict = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
NSString *key = @"someKey";
NSNumber *value = [NSNumber numberWithInt: 1];
//ARC doesn't handle retains with CF objects so I have to specify CFBridgingRetain when setting the value
CFDictionarySetValue(myDict, (__bridge void *)key, CFBridgingRetain(value));
id dictValue = (id)CFDictionaryGetValue(myDict, (__bridge void *)key);
//the value is removed but not released in any way so I have to call CFBridgingRelease next
CFDictionaryRemoveValue(myDict, (__bridge void *)key);
CFBridgingRelease(dictValue);//no leak

Answer 1

此处不要使用CFBridgingRetain和CFBridgingRelease。此外，在投射__bridge的结果时，您需要使用CFDictionaryGetValue。

CFMutableDictionaryRef myDict = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
NSString *key = @"someKey";
NSNumber *value = [NSNumber numberWithInt: 1];
CFDictionarySetValue(myDict, (__bridge void *)key, (__bridge void *)value);

id dictValue = (__bridge id)CFDictionaryGetValue(myDict, (__bridge void *)key);
CFDictionaryRemoveValue(myDict, (__bridge void *)key);

不需要CFBridgingRetain因为字典无论如何都会保留该值。如果你不打电话给CFBridgingRetain，你不需要在以后的版本中平衡它。

无论如何，如果您只是创建一个NSMutableDictionary，那么这就简单得多了，如果您需要CFMutableDictionary，请将其投射：

NSMutableDictionary *myDict = [NSMutableDictionary dictionary];
NSString *key = @"someKey";
NSNumber *value = [NSNumber numberWithInt: 1];
[myDict setObject:value forKey:key];

CFMutableDictionaryRef myCFDict = CFBridgingRetain(myDict);
// use myCFDict here
CFRelease(myCFDict);

请注意，CFBridgingRetain可由CFRelease平衡;您不必使用CFBridgingRelease，除非您需要它返回的id。同样，您可以平衡CFRetain和CFBridgingRelease。

如何在ARC中使用CFMutableDictionaryRef

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