error "Passing address of non-local object to __autoreleasing parameter for write-back"

Question

I'm converting my socket client to ARC:

- (id)initWithHostname:(NSString *)hostname AndPort:(NSInteger)port {     if((self = [super init]))     {         oBuffer = [[NSMutableData alloc] init];         iBuffer = [[NSMutableData alloc] init];          iStream = [[NSInputStream alloc] init];         oStream = [[NSOutputStream alloc] init];          [NSStream getStreamsToHost:[NSHost hostWithName:hostname] port:port inputStream:&iStream outputStream:&oStream];          ...     }      return self; } 

The error I got is:

error: Automatic Reference Counting Issue: Passing address of non-local object to __autoreleasing parameter for write-back

at this line on &iStream and &oStream:

[NSStream getStreamsToHost:[NSHost hostWithName:hostname] port:port inputStream:&iStream outputStream:&oStream]; 

Any help?

Answer 1

This error is usually due to the non local variable address is passed to a method. Because the variable is declared as __strong by default, while the parameter of the method is __autoreleasing, so declare the parameter of the method invoked as __strong,like this: -(void)method:(id * __strong *)param.

Note that the method in the header file (.h file) must be declared as the same of the .m file.

Answer 2

Create two local variables, pass the addresses of them to the the method, then assign their values to the ivars after it returns.