從常量無效*錯誤

Question

轉換無效我運行在.mm文件下面的代碼，我得到的錯誤：

Invalid conversion from 'const void*' to 'const __CFData*' 

我需要在.mm運行代碼。如果我更改爲.m它不會抱怨。爲什麼它的行爲如此？我編譯到iPhone

CFSocketNativeHandle native; 
CFDataRef nativeProp = CFReadStreamCopyProperty(theReadStream, kCFStreamPropertySocketNativeHandle); 

if(nativeProp == NULL) 
{ 
    if (errPtr) *errPtr = [self getStreamError]; 
    return NO; 
} 

CFIndex nativePropLen = CFDataGetLength(nativeProp); 
CFIndex nativeLen = (CFIndex)sizeof(native); 

CFIndex len = MIN(nativePropLen, nativeLen); 

CFDataGetBytes(nativeProp, CFRangeMake(0, len), (UInt8 *)&native); 
CFRelease(nativeProp); 

CFSocketRef theSocket = CFSocketCreateWithNative(kCFAllocatorDefault, native, 0, NULL, NULL); 
if(theSocket == NULL) 
{ 
    if (errPtr) *errPtr = [self getSocketError]; 
    return NO; 
} 

Answer 1

CFReadStreamCopyProperty()返回CFTypeRef，這僅僅是一個const void*typedef，和C++是約轉換比C（或目標C）嚴格。你需要在這裏明確地施展：

CFDataRef nativeProp = (CFDataRef)CFReadStreamCopyProperty(...);