Objective-C CF和OC之间类型转换

转载来源: http://blog.csdn.net/annkey123/article/details/8271806

1. __bridge操作符

__bridge操作符实现CF和OC对象之间的转换。

NSString* theString = @"Hello World";
CFStringRef cfString = (_bridge CFStringRef) theString;

2. __bridge_retained操作符

__bridge_retained操作符类同于__bridge操作符，但会给对象的保留计数器加1。

NSString* theString = @"Hello World";
CFStringRef cfString = (_bridge_retained CFStringRef) theString;

3. __bridge_transfer操作符

__bridge_transfer操作符与上面相反，将CF数据转换成OC对象，进行管理。

NSString* theString = (__bridge_transfer NSString*) cfStirng;