ARC and bridged cast

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I agree that the description is confusing. Since I just grasped them, I’ll try to summarize:

  • (__bridge_transfer <NSType>) op or alternatively CFBridgingRelease(op) is used to consume a retain-count of a CFTypeRef while transferring it over to ARC. This could also be represented by id someObj = (__bridge <NSType>) op; CFRelease(op);

  • (__bridge_retained <CFType>) op or alternatively CFBridgingRetain(op) is used to hand an NSObject over to CF-land while giving it a +1 retain count. You should handle a CFTypeRef you create this way the same as you would handle a result of CFStringCreateCopy(). This could also be represented by CFRetain((__bridge CFType)op); CFTypeRef someTypeRef = (__bridge CFType)op;

  • __bridge just casts between pointer-land and Objective-C object-land. If you have no inclination to use the conversions above, use this one.

Maybe this is helpful. Myself, I prefer the CFBridging… macros quite a bit over the plain casts.

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