<p>I have included <code>&lt;zlib.h&gt;</code> 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?</p>

<pre><code>"_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
</code></pre>

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.