CoreFoundation 类与 Objective-C 类桥

OC 转 CF

NSArray *anArray = @[@1,@2,@3,@4];
CFArrayRef aCFArray = (__bridge CFArrayRef)anArray;
NSLog(@"Size of array = %ld",CFArrayGetCount(aCFArray));

__bridge 的意思：ARC 仍具备这个 OC 对象的保留权。

NSArray *anArray = @[@1,@2,@3,@4];
CFArrayRef aCFArray = (__bridge CFArrayRef)anArray;
NSLog(@"Size of array = %ld",CFArrayGetCount(aCFArray));
CFRelease(aCFArray);

__bridge_retained: ARC 交出对象的所有权，使用完之后需要调用CFRelease()。

CF 转 OC

使用 __bridge__transfer

在CoreFoundation 创建字典

const void* EOCRetainCallback(CFAllocatorRef allocator, const void *value)
{
    return CFRetain(value);
}

void EOCReleaseCallback(CFAllocatorRef allocator, const void *value)
{
    CFRelease(value);
}

CFDictionaryKeyCallBacks keyCallbacks = {
    0,
    EOCRetainCallback,
    EOCReleaseCallback,
    NULL,
    CFEqual,
    CFHash
};

CFDictionaryValueCallBacks valueCallbacks = {
    0,
    EOCRetainCallback,
    EOCReleaseCallback,
    NULL,
    CFEqual
};
CFMutableDictionaryRef aCFDictionary = CFDictionaryCreateMutable(NULL, 10, &keyCallbacks, &valueCallbacks);
        
NSMutableDictionary *anNSDictionary = (__bridge_transfer NSMutableDictionary*)aCFDictionary;

Foundation层的字典，其键的内存管理语义是“拷贝”，值的语义是保留。
如果字典中加入新的键值，就会调用retain函数。
直接在CF层创建字典，就能修改键值的内存管理语义。