Defeating the "multiple methods named 'xxx:' found" error

Question

In my current project inside the file ViewController.m, running the method:

[[connection writer] writeData: data];

returns the warning:

warning: multiple methods named 'writeData:' found

I am attempting to call the method:

- (void) writeData: (NSData*)data

in TCPWriter.m. Unfortunately there are two other writeData methods

- (void)writeData:(NSData *)data;

in NSFileHandle.h and

- (BOOL)writeData:(NSData *)data

in NSURLHandle.h. This is especially confusing to me because [conn writer] should return the TCPWriter class and that class should call the correct writeData method. Furthermore I am not even completely sure that NSFileHandle.h and NSURLHandle.h are even included in any of the libraries included in ViewController.h, rather than in a different part of the project.

How can I show the compiler which writeData method I want to call and why does this error happen?

Answer 1

Make sure [connection writer] is actually returning a TCPWriter*. If it is returning an id, then the compiler will not know which writeData to use. Also, make sure you are importing the TCPWriter.h file - if the compiler does not see the header files, it will default to returning id, which will get you back to the same problem.

Try

TCPWriter* writer = [connection writer];
[writer writeData: data];

or

[(TCPWriter*)[connection writer] writeData: data];