linker - error when import zlib in iOS: symbol(s) not found collect2: ld

Question

I have included <zlib.h> in my iphone application and the source code I was mocking up the sample code of Molecules provided by Brad Larson, however, when I build the project, it returns the error as below. Can anyone point out for me whether this is a library linking problem or am I missing something else?

"_deflate", referenced from: -[NSData(Gzip) gzipDeflate] in NSData+Gzip.o "_inflateEnd", 
referenced from: -[NSData(Gzip) initWithGzippedData:] in NSData+Gzip.o "inflateInit2", 
referenced from: -[NSData(Gzip) initWithGzippedData:] in NSData+Gzip.o "_inflate", 
referenced from: -[NSData(Gzip) initWithGzippedData:] in NSData+Gzip.o "_deflateEnd", 
referenced from: -[NSData(Gzip) gzipDeflate] in NSData+Gzip.o "deflateInit2", referenced 
from: -[NSData(Gzip) gzipDeflate] in NSData+Gzip.o ld: symbol(s) not found collect2: ld 
returned 1 exit status

Answer 1

In your Target's Build Settings tab, scroll down to the Other Linker Flags section and make sure -lz is in the field. This will link against the built-in zlib, and your error should go away.

After changing the Linker Flags you must select Clean from the Product menu before building again.